An EQ would be nice, once you have the 6x9 and tweets swapped for a proper Comp set. I would first do that, see how it sounds and decide then if you want any more EQing then what the deck has, depending on the deck. As for the amp a 2ch. amp is fine if you just have the fronts to run, the rears are good with deck power. Do you have a sub in this set up? if not you could use the 4ch amp, but bridge the rear 2 ch to run a 10"...if you don't want a sub, save the bucks and stay with a 2ch on the fronts.

+1 again with Juleous and 90 ST.

I'd invest in a sub first before an EQ. You can usually get the sound very close to where you want it with proper placement (not many options in our small car), installation, and basic adjustments. The cabin interior is plenty padded and small; it doesn't sound like too many acoustic anomalies in it (I've yet to jam my spec analyzer in there to check). But in the end, if weirdness happens, EQ it. :D

If you are running your tweeters off head unit power getting any processor will not do any good unless you get a nother amplifier. You can't loop th eprocessor through the head unit power.

Why did you use 6x9 in doors and a nother set of tweeters in dash?