I just finished putting together a system for my Lexus ES300. The car has a good sounding stock stereo in there so I didn't go after speakers right away. After a good head unit, 2 12's, and an amp Im low on cash. Are new 6.5's and 6x9s neccesary for it to sound ok? The car has a premium sound system and good speakers, so I think I might be alright.