Hey Paul!

Yes, Paul is right. Rears, if you want them back there, should just barely be heard. Subs give you foundation bass, so that is another consideration... but your rear speakers are just for fill.

I set up my amp by turning the gain all the way down, and any bass boost or whatever off. Then, turn your volume up to where you hear distortion in the speakers (which ever you are setting up... front or rear), then turn it down to 3/4. Now, turn the gain up to where you hear distortion, then back off a bit to where they sound clean.

I installed my Crystal CSX615's yesterday, and they are too large. I started routing the OEM speaker baffle just to get them in, and ended up gluing some weather stripping around it to seal the space between the speaker and the baffle. After installing them, the door cladding won't go on all the way by the speaker... and the bass rattles the cladding too much. They sound good, but they are just too large. I may sell them and go with something a bit smaller.