Stereo Help!

Here's my situation.. I have a 2002 Accord EX Sedan. While the sound is pretty decent I'd like to improve the quality of sound. I asked an employee at the Good Guys and he told me that the system was 15 RMS or 20 at the most. I'm not sure I want to buy an amp and sub just yet. I was just looking to replace the head unit as well as the 6.5" and 6x9 speakers. My budget is somewhat open but I want something that will be the best overall value. I listen to mostly R&B, Rap, and Techno. I also occasionally listen to Alternative as well.

I'm not sure which receiver I should get. If I end up not getting an amp, I was looking to get one of the Alpine head units with the 60x4 watts. However, I was also looking at some of the Sony receivers.. the ones with the cd try that comes out. I heard that those skip because it's a tray. How are Alpine and Sony in general for car audio? Are there any head units you would recommend that are under $400?

As for the speakers I was looking to get the Infinity Kappa's for both the 6.5" and the 6x9. What do you think about that idea or are there any other speakers you would recommend? In the future I may get a sub and amp, but with the current setup: Alpine 60x4 head unit and Infinity Kappa's all around I'm hoping to achieve a better sounding unit with some more bass. Do you think this setup would okay for that? Also, if I were to get an amp later on, is there any you would recommend? Preferabbly nothing over $300 or so. As for the subs, I may or may not get them later on. I've seen many subs but am turned off by the large amount of space they take up in the trunk. I saw an article about the MTX Thunderforms and thought that I might get that if I were to ever get subs. What is your opinion on those?