I have done this many times on the CI side and recommended it to dealers since moving to the rep side. There is a little hacktastic to do on the XLR as you need to remove the heads on one side. You also want to make sure you sum at the euroblock connection as I am guessing you want summed to the sub and the sats and most of the DSPs built for the Crown amp will expect the signal to be summed prior to input.
Jack Rainey - Full disclosure...reformed integrator, now mid-Atlantic manufacturers rep for: Integra, Paradigm, Anthem, Parasound, Atlona, LG TV's and Metra Home Theater...among others