Infinity Kappas are popular for a reason : )

Just to let you know, I drive a 95 Mazda MX-6 which has similar airspace to your car. Of course YMMV.

First, I am going to give you a bit of advice that some on this board might disagree with, however I would advise you to use your own judgment. Ditch your back speakers. All they do is ruin you soundstage and waste your money. They do nothing to improve imaging (music is recorded in stereo (2 speakers) not quadrophonic (4speakers) and even if it is the empeg can't output it (i think). Connect the 2 front outputs to the amp for your fronts and use the rear outs for you sub.

For fronts I have (drum roll please......) Infinity Kappas! I have a Profile amp pushing 100 watts RMS to each of them (make sure to look at the RMS rattings as it is the only one that comes even close to mattering). This is THE RMS rating for the speakers. You can go less but not much higher than the rating. Since it is RMS (Root Mean Squared) it is an aproximate rating so you don't have to be exact. Best shoot for an amp in the 50-110% of your speaker's RMS rating.

For the sub I have an Infinity Perfect 12" in a sealed box that came free with it from crutchfield. Thats right, only one sub. Low frequencies are not directional so you dont need stereo for them. It is better to go with one really good sub than 2 cheap-o's. Now, this sub is rated at 300 watts RMS and something like 1200 max. I have a (seperate) Profile amp pushing 400 watts RMS at it. "But Marcus....thats 100 watts over it's rating!". It's in a smallish sealed box, its an Infinity, its been running fine for the past 9 months. It can handle it if it is tuned properly. (More on this later.)

I have the crossovers on the amps set to 85 Htz (the fronts getting the high frequencies, the sub the lows obviously). This seems to work very well for these speakers. One thing you will love about these speakers (especialy for rock) is the nice even lower frequency responce throuout the mid and lower bass ranges. People who are used to listening to people's one note wonder boom subs marvel at the smooth responce of my car. (Its not perfect, but better than most have heard).

On profile amps:
They are cheap, they work as good as any. That about sums it up. Used to have problems in the past, but they are over that. SQ is great. You would have to spend a LOT more to get anything signifacantly better, and if your not used to listening to ultra-high quality sound setups you probably still wouldn't notice much of a difference.

Total system cost for me (sans empeg) was $750 shipped. Right at the bottom of your budget and it just blows me away. So how does that sound for you?

Thats all I have time for now. I'll try to post more about setting gains and such (crucial to getting your system to sound right) later. Feel free to ask any questions.