My suggestion is to completely forget adding an amp right now. Because that money could be used towards your speaker budget for something you really enjoy. You might not need the extra money there, but if you did, it might allow you to get your favorite thing when it comes to that time.
What's your budget?
I've seen and heard McCormack stuff, but the speakers are vastly more important than choice of amp.
Also, and I've owned both, I trust NAD amps much more than I do their pre/pro sections. I don't have scientific data, and I can't even say for sure subjectively, but it's possible that my old unit had a lot of distortion, at least via digital inputs.
What I'm trying to say is that your NAD receiver might be plenty for the speakers you choose. Get speakers first, then figure out the levels you listen to, the difficulties/loads that the speakers present, how far you sit from them, etc.
Run a couple of search engine exercises on "Salk" at this subforum.