You have the hookup process exactly right, yes. Since the interconnects between your receiver and the new amps will be used at all times for the main channel, using cables that produce a good connetion is more important there.

You'll want to use the new amps to drive the mains all the time. If you're concerned about smooth blending between speakers, you'll probably be fine, but you might add a 3rd M-Block for the center channel (that's what I did with my 3802) and let the receiver drive the surrounds.