Control amps: suggestions needed

Yeah put a Mac with a cheap Yamaha.

Or start over.

What's his budget? Maybe find something cheap on eBay or USAM?

The inevitable question.  I haven't asked that of him.  I was hoping to just throw a bunch of suggestions at him (with commentary) and let him rise (or sink) to the level he feels comfortable.  I think he might choke at $1,000, so aim at lower than that.

I was hoping to be able to winnow the universe of control amps down based on what might get suggested here.

Based on what I get as suggestions, I've been toying with the idea of proposing a FET-10, coupled with a Loki mini, a Loki mini+ or even the Loki Lokus and let him sort it out.  I think he would go for the Mini if he buys the idea at all.  A used FET-10 might deter him, I think, based on the price.  He loves mine.  But then again, I have better amps and speakers too, so it's stacking the deck.  Based on what I've read, I might add a Loki to my system.  Probably the Mini+ if I do.  I don't need remote control.  But then again...

The matching preamp is Yamaha CX-600.

Move away from low-line commercial products and get a quality integrated amp like a Musical Fidelity. 

Considering he got the Yamaha only a few days (like 2 or 3), I don't think he would look kindly on that suggestion  In essence I agree with you.  I tried top talk him into better equipment acquired more slowly.