Quick summary of Outlaw's five-channel amps:
- Model 750: 5x165W, introduced in 1999 I believe (Outlaw's very first product)
- Model 755: 5x200W, sibling of the 770 (7x200) and replacement for the 750, introduced in 2002 around the same time as the Model 950
- Model 7500: 5x200W with balanced inputs, sibling of the 7700, introduced in 2005 to match up with the Model 990

I used my Model 750 for the better part of five years, with three different processors (a Model 1050 receiver, a Model 950, and a Model 990). While the 7500 definitely offers some sonic improvements (particularly for two-channel listening at higher volumes), it is a case of diminishing returns. Upgrading from a 750 to the 7500 will cost a pretty penny (even after selling the 750 to fund the upgrade), so you've got to weigh those improvements against the cost.

The Outlaw PCB's are well-made, sturdy cables - but cables are cables, and if it weren't for the fact that the cheap cables I got initially were way too long for my application I doubt that I would have changed. I do not believe that there is a sonic difference between the two, but at least one of the connectors on the cheap cables was uncomfortably stubborn about connecting and disconnecting from the 7500, whereas the PCB's connectors were very well behaved about sliding into place (although they did take a bit of a push to lock in at the 990).