QSC has a reputation of being on the lower rungs of gear in the pro world. I had bought two different models of amps about 10 years ago and promptly got rid of them. I kept the lower powered but better sounding Crests (I looked around at what some of the good local venues were using for sound reinforcement - concert halls, etc.) The QSC units were craptastic unsuitable for hifi. Maybe for part-time DJs at third-tier dance clubs. I don't think the mx line is one of QSC's top lines either.
Of course this doesn't mean the QSC isn't better than the NAD or Marantz. However, I never understood why NAD was considered to be great or even a good value. In the 90s, I went through two successive NAD amps, neither of which stayed in my system for more than two months. After I realized how shitty they sounded compared to a vintage late 70s Sony 20WPC receiver, I swore never to get another NAD amp again. Maybe they are different now, but I'm thinking their heyday was before the 90s and their heavy advertisements on their BSy "dynamic headroom" technology and heavy shilling by Crutchfield in the Crutchfield catalogs.