Well my replacement Mainstream arrived and I had it plugged into the ZLC for a few hours and sat down to listen.

Wow. It really does make an improvement, even with the LNBHs and Zero in place. It makes me realize that the ZLC is a great centerpiece for all this to be plugged into, and although I will try doing without it I think it is probably going to be kept in place to power the LNBHs and the Zeros and the Snubway and the Mainstream. I am getting amazing sound right now in this congiguration before the second Zero arrives.