Bob-O -- the 755 and the 750 will look the same, for what it's worth, although the 755 will be a couple inches deeper. Aside from the depth (the 770 and 755 are deeper than the 750), all three amps are the same size. Or if you want/need to maintain consistent power rating to everything, you could either 1) sell the 750 to help buy a second 755 or 2) look for a second 750 used.

There's nothing officially announced to prove it, but here's what I've assumed -- the 770 is Outlaw's first seven channel amp (7__ = amp, _7_ = number of channels, __0 = first of the type), but the 755 is the second five channel amp. (Plus the fact that the 770 had been announced before they decided to borrow from it to create a replacement for the 750, in all likelihood, meaning it was too late to call the 770 the 775.)

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Gonk