My advice would be to first determine a budget because you can get higher quality speakers if you plan right. I have Kappa 3 ways in my rear doors and they provide rear fill just fine.
I also bump a Perfect 10 and I think it's very respectable as far as subs go. Sure there are "better" subs, speakers, amps, etc...but whatever sounds good to you is the best!
I used to think Infinity speakers were the best sounding speakers because I was listening to them side by side with Pioneer and Sony...now that's crap!! So I guess I would say, in my current state of car audio evolution, that Infinity makes the best of the crap! But hey, like they say...opinions are like assholes, we all got em and they all stink!
Pick yourself up a set of some Boston Z's for the low low price of $1000 and I'm sure you will be happy. Again, it's all about affording the best sounding set of speakers in your price range.(headbang)