A bad idea. Balanced amps require an inverting and a non-inverting signal. I know trying to do that with an ARC amp results in half the amp output and higher distortion because you are only driving the amp with a non-inverting signal. The inverting side of the signal doesn't exist so that part of the circuit is not being driven. ARC did at one time make a powered device the took an RCA single ended input and gave you a real balanced output. You might want to consider something like that, or a good used balanced output preamp.
XLR to RCA Adapters
I am interested in a BAT amp but my Rogue 99 Magnum does not have balanced outputs. There are of course adapters (Cardas makes what appears to be a nice one), are these worth it or do they defeat the purpose of a balanced unit? Do they compromise sound quality?