Perfect system is:
JL Audio Subs
Fosgate Amp
Alpine Deck
Speakers are a little tougher, I have heard a lot of different ones, and I do like Pioneer they make great products, Xplod sucks don't get those at all, haven't heard of Infinity, Kicker is pretty decent too, but I wouldn't buy more than two speakers, the tweeters with the subs sound fine, then again some music concentrate a lot on mid's so four wouldn't hurt. I would have to flip a coin between pioneer and Kicker, both, from my experience are awesome speakers.
SIDE NOTE: I have had my Omega Diesel amp for over a year now, the thing has never overheated and I play my music loud, the only problem I have ever had is a wire came loose and the light in the middle of the sub doesn't light up sometimes, but who cares, the thing still makes my subs hit.