I just got a new (used) Toyota Tacoma and have started building a new system for myself. That being said I've spent a good deal of my spare time going from shop to shop listening to 5.25"s myself. My best advice is for you to do the same. Everyones tastes are different and what sounds good to me may not sound the same to you. Bring your own CD when you go - no sense in demo'ing a speaker using music you don't necessarily like

My findings were: The JL Audio XR series blew me away! Specifically the XR525-CSi's. The 6.5"s sounded even better but they won't fit without more work than I'm willing to do. The JL VR Series sounded good too but not as good as the XR's. The Polk DB's and the Infintiy reference's sound about the same with the Infinity's winning out based on power handeling. I didn't find any Kappa's to listen to and therefore couldn't consider them. Boston Acoustics had some good sounding offerings but only in their Pro series ($$$!) The Alpine S and R series sounded like the cones were too "heavy" (couldn't find any 5.25"s anyway.) I didn't listen to MTX's. The Sony's and Kickers sounded terrible.

I ended up spending a little more for the XR's. In all ~$210 on ebay including shipping. Keep in mind that heavily discounted prices on ebay usually mean NO manufacturers warranty. With some proper tuning of the system I'm sure I can get them to sound even better than they did on the demo board.