I got the Polk db series full ranges in mine, they sound great,Ditydog's advice is good,listen to him on audio matters.

 

If you don't want to add in an amplifier, then I would say that you should be looking at Infinity Reference series. The RMS requirement is low enough that the H/U can push them efficiently and you'll have a nice gain over stock.

Personally, I run Infinity Kappas and Kappa Perfects (Old school infinity)

Alpines, Polk, Kicker, and JL (Meh) are all Decent. (That is my order of preference. Never liked JL all that much but some people do.)