I haven't seen a 7500 or heard one so I have no idea of either the topology of the new amp or what it sounds like. If it is similar to the 755 with only the addition of balanced inputs, I'd say the sonic differences should be minimal. If you're not getting induced noise through your cables, having the ability to go to balanced connections doesn't strike me as being a very useful reason to spend that kind of $$$ to "upgrade."

Cheers,