I use the MixIt2 and I'm satisfied with it.
I had originally inserted it right behind the gas tank, in the void behind the engine. That proved to be too close to the ignitions and I could heard the clicking sound driven by RPM. I then relocated it near the tool bag under the rear of the seat and that works great. It comes in a bubble wrapper, so I just plug the wires into it, immobilize it but left it in the bubble to help protect it.
I adjusted the audio level to what I wanted to (radar detector; GPS; and XM are limited as far as adjustment goes; and my MP3 is handling it nicely) and just leave it there. I ran an extension for my earbuds so I only have to plug in one thing when I saddle up.
Not cheap, but it's good stuff.