As Leigh suggests, a good lager kit and some saflager will put you in the right direction. As for a dopplebock (double bock), well, we need to get some serious malt and hops involved as well as non-kit yeast if we're going to get close to that glorious offering from Spatens (I'm currently going through a dunkelweizen doppelbock phase with Erdinger Pikantus - it's truly stuff from the gods!)...
So, lets get our bearings straight - what are the BJCP guidelines on dopplebocks:
5C. Doppelbock
Aroma: Very strong maltiness. Darker versions will have significant melanoidins and often some toasty aromas. A light caramel flavor from a long boil is acceptable. Lighter versions will have a strong malt presence with some melanoidins and toasty notes. Virtually no hop aroma, although a light noble hop aroma is acceptable in pale versions. No diacetyl. A moderately low fruity aspect to the aroma often described as prune, plum or grape may be present (but is optional) in dark versions due to reactions between malt, the boil, and aging. A very slight chocolate-like aroma may be present in darker versions, but no roasted or burned aromatics should ever be present. Moderate alcohol aroma may be present.
Appearance: Deep gold to dark brown in color. Darker versions often have ruby highlights. Lagering should provide good clarity. Large, creamy, persistent head (color varies with base style: white for pale versions, off-white for dark varieties). Stronger versions might have impaired head retention, and can display noticeable legs.
Flavor: Very rich and malty. Darker versions will have significant melanoidins and often some toasty flavors. Lighter versions will a strong malt flavor with some melanoidins and toasty notes. A very slight chocolate flavor is optional in darker versions, but should never be perceived as roasty or burnt. Clean lager flavor with no diacetyl. Some fruitiness (prune, plum or grape) is optional in darker versions. Invariably there will be an impression of alcoholic strength, but this should be smooth and warming rather than harsh or burning. Presence of higher alcohols (fusels) should be very low to none. Little to no hop flavor (more is acceptable in pale versions). Hop bitterness varies from moderate to moderately low but always allows malt to dominate the flavor. Most versions are fairly sweet, but should have an impression of attenuation. The sweetness comes from low hopping, not from incomplete fermentation. Paler versions generally have a drier finish.
Mouthfeel: Medium-full to full body. Moderate to moderately-low carbonation. Very smooth without harshness or astringency.
Overall Impression: A very strong and rich lager. A bigger version of either a traditional bock or a helles bock.
History: A Bavarian specialty first brewed in Munich by the monks of St. Francis of Paula. Historical versions were less well attenuated than modern interpretations, with consequently higher sweetness and lower alcohol levels (and hence was considered "liquid bread" by the monks). The term "doppel (double) bock" was coined by Munich consumers. Many doppelbocks have names ending in "-ator," either as a tribute to the prototypical Salvator or to take advantage of the beer's popularity.
Comments: Most versions are dark colored and may display the caramelizing and melanoidin effect of decoction mashing, but excellent pale versions also exist. The pale versions will not have the same richness and darker malt flavors of the dark versions, and may be a bit drier, hoppier and more bitter. While most traditional examples are in the ranges cited, the style can be considered to have no upper limit for gravity, alcohol and bitterness (thus providing a home for very strong lagers). Any fruitiness is due to Munich and other specialty malts, not yeast-derived esters developed during fermentation.
Ingredients: Pils and/or Vienna malt for pale versions (with some Munich), Munich and Vienna malts for darker ones and occasionally a tiny bit of darker color malts (such as Carafa). Noble hops. Water hardness varies from soft to moderately carbonate. Clean lager yeast. Decoction mashing is traditional.
Vital Statistics:
OG: 1.072 - 1.096+
FG: 1.016 - 1.024+
IBU's:16 - 26+
SRM (Colour):6 - 25
ABV: 7 - 10+%
Commercial Examples: Paulaner Salvator, Ayinger Celebrator, Spaten Optimator, Tucher Bajuvator, Augustiner Maximator, Weihenstephaner Korbinian, Weltenburger Kloster Asam-Bock, EKU 28, Eggenberg Urbock 23°, Samichlaus, Bell's Consecrator, Moretti La Rossa
Bocks and Doppelbocks aren't the easiest beers to make, so let's be realistic about what we can achieve with a kit - and don't take that as a slight on kit brewing, it's just the reality of the situation...Anyway, I'd look at a Bavarian Lager kit or equivalent to start off with - I'm sure that any dark lager kit would be good but I'll use a Coopers Bav Lager kit since they're widely available.
Colour is easy - Dark malt extract is the go - but that won't give you the melanoidins or slight choc notes that a true doppelbock has. And to be honest, you basically have two choices to address those flavour issues - steeping grains to get close, or doing a partial / mini mash to get even closer.
If you're steeping grains, I'd steep 300g Caramunich II, 500g Dark Crystal and about 100g of Carafa I or Choc malt in 6L for a 23L batch - and add about 4kg of light liquid malt extract and the Bavarian Lager kit (or save some money and just buy 6kg of malt extract), since you're looking at a starting gravity of 1.085 to be in the zone...
A mini or partial mash gives us more scope to hit the bullseye - I'd mash some Vienna, a good lump of Dark Munich and some Melanoidin Malt along with a dash of Carafa I or Choc malt.
As for hops, you need to use a German noble so I'd boil about 60g of Hallertau in an 8L boil with the steeped grains - gently add the malt extract / kit after the 30 minute boil - you need some decent IBU's in this to balance all that malt so don't have too much sugar / malt in the boil which will lower the hop bittering potential of the short boil. You've mentioned your disappointment with sweetness so keeping the boil ingredients to just the steeped grains will result in a well bittered small boil that will help balance out the massive malt bill in the recipe - doppelbocks are big beers that need plenty of lager yeast to get through all those sugars.
As for yeast, you need a decent lager yeast for this big wort - if you don't have temperature control, then you can make do with San Fransisco Lager yeast (White Labs WLP810 or Wyeast 2112 California Lager Yeast) that works well at 18-20C but beware that it's highly flocculant so you may need to rouse the wort on occasion to finish it off.
If you have a nice cold corner in the garage or you have a temperature controlled fridge for fermenting lagers, I'd recommend Wyeast 2124 or 2206 and make sure that you have at least 1L of starter to get through this big brew.
If we're on a budget or we're limited to dry yeast, two sachets of W34/70, or S-189 or S-23 will do the job.
Hope my musings are of help...
Cheers,
TL