I see what you are trying to do. The control of the krell for the lows and the purity of the 750's for Mids and Highs, I do the same on my Schweikert vr-8.
The Main thing is make sure you have a way of adjusting sensitivity of the input drive to the amps.
I tried this with a tube amp and Mark Levinson for the lows, Never could get the sensitivities correct.
That ARC will sound better the the krell