Since I've only got a Model 750 (although I may pick up a couple of 200's eventually), I can't speak first-hand to the sonic differences between the 770/755 and the 200, but there is a Model 200 review by someone who replaced a 770 with seven 200's and reported no sound difference -- so it seems pretty likely that you would not hear a difference between 770 and 755+200's. The 770 would cost you less overall and would use less cabinet space, but the 755 and 200's would spread the cost out. If you think it is likely that you'll go to seven channels in the not too distant future, I'd lean toward getting the 770 and letting two channels sit idle for now.

------------------
gonk -- Saloon Links | Pre/Pro Comparison Chart | 950 Review