It will depend more on your amps, but I would install the 10ga so that if you end up with amp(s) that are really power hungry you WILL get better sound out of them. I have four dedicated lines to my room, one for each mono amp, one for analog (pre and phono) and one for digital/mechanical (CD and TT). I let the CD and TT share since they are never used, or on, at the same time. This might be over kill, but at least with my system, I do hear a difference versus 12ga. YMMV.
Good listening,
Mike
Good listening,
Mike