since no one else suggested anything...
I'd suggest goto your local car stereo shop and tell them how much you got to spend.
don't goto best buy, circuit city, or those mainstream stores...
solitary shops that specialize in car audio know best, and they get the newest stuff on the market first.
I'd stay away from brands such as Audiobahn and Sony Xplode (known for problems in the past).
I've had great experiences with
Lightning Audio (subsidary of Rockford Fosgate, alright quality, low price ~$99 for 400 watt)
Koiiler (great quality, good price ~$120 for 600 watt) http://www.koiiler.com/
Currently, I have 2, Almani audio Amps (ALCH 550, $120) and (CA1200, ~$200, I paid $120 because I did some work for him), and they are great.
The next step up would be JL Audio, Pioneer, or Alpine equipment, but that's asking for more money.
what size l7's? all in one box or seperate? are they going to be wired parallel or series? If you have the 4ohm dvc in series your amp needs to handle at least 2.67 ohm, 2ohm dvc then 1.33ohms. If in parallel three 4ohm dvc requires 0.67ohm handling from the amp, 2ohm dvc requires a very unstable 0.33ohm handling from the amp. More here
Three 12's (750 each) 2250 rms watts
Three 10's (600 each) 1800 rms watts
If they're 12's and 4ohm dvc wired in series then the Kicker ZX2500.1 is a nice choice. This same scenario with tens and the ZX1500.1 will work nicely. Or, you could get an amp for each sub.
Once we figure out your exact setup we can make more suggestions.