So I'm working on my car stereo to try and get a good system going. Right now I've got a Sony 55w CD-player running a pair of 6 1/2" Infinity Kappa Perfect 6.1 speakers in the front. The rest is stock (no amp, no sub), and I've got 6x9s in the back. The next step is to get an amp and a sub, and then some speakers for the back. The wonderful speakers up front sound pretty weak right now without an amp, so that's definitely first priority. Sound quality is the most important thing I'm buying for, so do you all have any recommendations for amp and sub (10")? I'm pretty sure that I'm going to get the Infinity Reference series 3-way 6x9s for the back. There are probably more expensive options but I've always been under the impression that back speakers don't need to sound as good as front speakers as they're mostly just filler. I'm afraid I might have to run two amps for speakers & subs.