I've been running a Resonant Engineering RE-SE12 (600 watts RMS with 4 ohm DVCs)sub with an Audiobahn Intake 8000T (800 watt RMS @ 2 ohms) for a while now, and have been very happy with its performance. After a few different builds in other cars using ported and bandpass enclosures, i've been most impressed with the crisp clean quality of sound acheived from using a well sealed enclosure. Ideal for this car in my opinion would bee right on 1000 watts RMS with a hardy 15" 800+ watts RMS sub (if you can afford a JL sub with power handling over 500 watts RMS, by all means, do it).
BTW, I've been happy with the stock infinity door and rear quarter speakers, I have not changed them out. They are running on my Audiobahn Intake 6004 amp (50 watts RMS x 4 channels) along with a pair of 3/4" crossfire dome tweets mounted where the stock ones were.
I have been tweaking this system for months, and it still impresses me with the quality of sound it puts out. With some passive crossovers and rewiring my tweets to my deck, and adjusting some gain levels, i can squeeze out some even better sound, but haven't had the time and resources lately. Keep us updated on the system build, its always fun to see what everyone's up to. Any roadblocks, let me know, I'll see what i can do for you joshuadfoster@yahoo.com