Just installed the polk 5x7s that I got in the mail today, along with some technics tweeters I had lying around. The sound is amazing now. Both the highs and lows are incredible. I do not need an amp for the four main channels. However, I will continue to consider a subwoofer. I'll see what kind of money comes my way after Christmas. One question, Pointdablame: How powerful do subs have to be to be effective? My stock HU puts out 18 watts per channel, 30 watt peak. Right now with the new speakers, it sounds louder than my 200 watt home system with floor speakers. There is a good deal of bass, much more than with the stock speakers, but not up to what I was hoping for. I found a deal on a pair of Jensen 10" woofers in an enclosure, 35hz to 300hz, at crutchfield. I think they are capable of 150 watt RMS each, with a 300 watt peak. Assuming I get an amp with matching specs, what can I expect? I don't really want ear shattering bass, but just somewhat more than what I have.