I have the Boss MC400 system on my Vegas 8-Ball. The sound quality is great. If I keep the visor on my full face helmet cracked I can hear it with no problems even at highway speeds. If you don't wear a helmet or use a half-helmet sound won't be an issue.
It has a nice volume knob that I installed in the speedo bracket so it is easy to reach. The brackets it comes with are designed to mount on the mirror bolts. I'm sure they can be mounted other ways also.