I used the Infinity Kappa 3.5" in front in the speaker bracket listed in the new deals section.
The speakers sound great for their size. Any 3.5" speaker is not going to have very good bass response. The rear speaker shelf should be able to use 6x9" speakers. In my convertible, I used 6.5" round speakers in the rear arm rest panels. With the top down, it was still hard to get good low bass, so I put an amp and sub in the trunk.