The ZD engineer said it is possible to make use of both pre-amp types, but that:

The only exception would be an input selector switch on the power amp selecting balanced, or unbalanced, but not both at the same time.

I think he prefers the simple route, either (990) or (ZD).

It's unfortunate because each listening experience is very different from the other, yet both desirable. What it would cost to have the amp changed, in this way, with such an input selector switch, is not something I have any idea about.

The best way is probably to pull the main speakers out of the HT setup, separating the two systems. For now, I'll leave it as it is (it’s complicated enough, already).

I appreciate the responses and suggestions.

Gonk, I’m glad to hear you’re doing fairly well, improving and getting stronger. I’m not surprised to hear that your daughter is enjoying school, and the fact that she's going should also makes things a little easier for you. I can imagine your impatience, regarding your inability to drive; but, hey, why not take advantage of it, enjoy the opportunity to let others do the driving. I’m sure it won’t be too much longer.

And, good luck with the surgeon; I hope he has more good news for you!

John