i usually run PolkAudio DB's. they're low budget yet sound very clean. it's not super bright or super boomy so you get more of a flatter (it's not flat) response and fine tune your sound with eq to finish it up.
im going to be doing the 6.5" this spring. need the temps warmer so i dont shatter anything... ive learned my lesson on another car long time ago. hahaha.