You can certainly use an XLR-RCA adapter to feed your amp a single ended signal. Just put them on the input to the amp as Tvad says. However, you would lose the noise rejection benefit of the balanced cables. You can't have it both ways.
The noise rejection comes from the fact that the cables are balanced and any noise that is picked up will be equal in both lines. This noise is then cancelled at the input to the amp, but most home listening rooms just don't have a level of electrical noise that is worth worrying about so I doubt you would hear any increase in noise.
The noise rejection comes from the fact that the cables are balanced and any noise that is picked up will be equal in both lines. This noise is then cancelled at the input to the amp, but most home listening rooms just don't have a level of electrical noise that is worth worrying about so I doubt you would hear any increase in noise.