Old NAD v New Marantz

Hi all. Opinions wanted. I've had a NAD T747 for years. When I bought it, it was used for stereo, as well as HT.  I now have a pretty good 2 channel system (Anthem, Maggies, etc.) and want to upgrade to an Atmos capable HT system. So the question: would I lose much in terms of sound quality with a high (ish) end Marantz (maybe a 7011) or Denon? 

At the moment the HT speakers are small Athena (remember them?) which would also be upgraded in the future.

Thanks in advance.