I would agree that if your room conditions or choice of equipment induce hum, then balanced cables come in handy. For the 3ft run between my 990 and 755, RCA connections are just dandy.

Nothing personal, but I just find it amusing that anyone would pay 1500-2000 per PAIR of balanced cables (MIT Oracle 3.2). That means the cabling between your 990 and 7500 exceeds the cost of the actual equipment (assuming you're using 5 channels) by a fairly wide margin. When I need balanced cables, I just roll my own out of Canare star quad mic cable and Neutrik XLR connectors. Perhaps I'm just in the wrong business. :-)

Best,