system options need 2nd, 3rd, opionions

I've built several nice systems, but in today's economy, I'm at a point where I dont have the blank check to get whatever fills the bill. I have a head unit that is 20 x 2 RMS with 2 ch pre outs (there is a possibility I can pick up/trade for a buddies 4ch pre out HU if need be). In the front doors are Boston Acoustics 4" - in the back, Boston 6x9's. I more than likely will not be adding a sub (room, cost, etc). I find the BA's handle the bass enough I don't mind. I guess my questions are: is the 4ch pre-out necessary for a decent system? Also - if I add an amp (which I think is necessary as BA's are power hungry), I don't have alot of room to mount one, so a 2 or 4ch would have to be nominally sized, in the area of 8x10x2. You guys have forgotten more than I've known - so thanks for any input/suggestions.Subtlety is EVERYTHING.

What kind of Car,Stereo,Stereo you might trade for...?M.E.C.P & First-Class

Go slow and drink lots of water...Procrastinators' Unite...Tomorrow!

Its a sightly older Alpine.....exactly like mine only 4ch instead of 2ch.Subtlety is EVERYTHING.