Well, heres the kicker

stock headunits, 98 percent at least, attenuate the bass as you turn the volume higher, as to not have people blow the speaker sin the first couple of weeks of ownership, ya dig?

so if you upgrade to a new HU, odds are you will need to upgrade speakers, if nto soon...

but they stockers will work fine for a while if you wanna hold off for a bit

but back to the matter at hand:

Alpine has some pretty solid 200 ish level recievers, as do kenwood

pioneer lower level stuff is almost worthless for me, but if you like it then go fo rit

for 6x9's, JL audio, or you could get some other speakers, like 5.25's, build a panel to fit anf put those in there...