I see no reason to second guess your choice of amps. Balanced inputs are borrowed from the recording studio, where they are used to cope with the high levels of background interference that can exist (particularly over longer runs). You do not need balanced inputs on your amp to use the 990, although those of us with unbalanced amps will want to use the unbalanced outputs and simply leave the balanced connections alone. I expect a significant majority of Model 990's will be connected to amps with unbalanced inputs (such as your Model 7100). Some people will use the balanced outputs because they have gear such as EQ's downstream of the processor that use balanced connections or they already own amps that have a balanced topography.