I second the PC4 idea. It was designed by McIntosh for exactly your application - it even has staggered on-delays. Top quality too, of course.
I have my MC7100 plugged into the back of my C712 (great combo BTW - you will love yours, I'm sure) with no difference in sound than straight into the wall. I have compared the two ways at length and don't find any reason not to plug the amp into the preamp. The power rating of the preamp's switch is ample for a 7100.
Enjoy your great little setup! Arthur
I have my MC7100 plugged into the back of my C712 (great combo BTW - you will love yours, I'm sure) with no difference in sound than straight into the wall. I have compared the two ways at length and don't find any reason not to plug the amp into the preamp. The power rating of the preamp's switch is ample for a 7100.
Enjoy your great little setup! Arthur