RCA vs XLR which would say is the BEST?????

Lots of variables. Depends on the electronics. There will be a sonic difference just in using different cables. In my experience comparing same brands of cables (1m lengths) RCA is just fine, no benefit from XLR balanced cables.

If a component is truly balanced do it, if not it doesn't matter much and in fact the single ended(RCA) may sound better. I don't hear many people using truly balanced components claiming they sound better when running single ended cables. Having said that I prefer balanced components with balanced cables.

I second Tim's post.

Bryston is a great amp, but it is not truly balanced, and you are not using long lenghths so RCA's are just fine.

I recently set up a sound system for an event at our church. I got everything up and running, then finished running some cable. I ran a cable with single ended 1/4" plugs about 20' across the floor. Soon after that I noticed a hum. It did not take long to determine that this cable was picking up an induced hum from an extention cord that was running next to it. Separating the audio cable from the extension cord solved the problem. However, I tried running a balanced cable next to the extension cord, with a 1/4"/balanced adapter plug at the source end. This also solved the problem.

The point is that there is some benefit from running balanced in that it can reduce background noise. Noise is the curse of many audio systems, and I think one reason balanced cables sometimes sound better is due to reduced noise. But you can also do a lot of good by not jumbling all the cables, power and audio, in a pile behind the equipment. Separate the cables, or at least make sure they do not run parallel to each other.

Happy listening.