Are you telling that Denon 4311 or Yamaha 3010/3000 are better than Anthem MRX in overall sound quality?
No, but they, for example the Denon has a better feature set including 11.2 pre-outs, preamp mode, 4 ohm capable, and I trust the Denon's Audyssey XT32 more. The Denon also seems more powerful but most likely too negligible to make a difference.
Anthem MRX 700 A/V Receiver HT Labs Measures | Home Theater
Denon AVR-4310CI A/V Receiver HT Labs Measures | Home Theater
I cannot find a review of the 4311 by HTM but I have read a couple by others including one by Home Cinema Choice. I trust HCC more.
I could definitely spot the difference between, Elite SC-37 with my friend's Denon 3808. Also, I always felt that Yamaha is little bit bright (I listened RX-V3800/3900 many times, but never listened to the new A series).
I know you say "definite", but I still wouldn't be so sure because it is very difficult to do a proper A/B comparsion and to be credible you really need to do a blind test if not double blind. Besides, the SC-37 uses the ICE class D amp so it may also be possible that it could sound slightly different under certain conditions.
Anyway, if you are happy with either one that's great just don't assume they will sound better because some people/reviewers tell you so. I am not trying to talk you into considering Denon and/or Yamaha. I am just trying to tell you AVRs within the same price group just don't sound noticeably different and if driven within their power capability they don't even sound different than separate systems that cost twice as much or more.
You felt the 3800/3900 sounding bright probably because the units you listened to was not set to pure direct? Or it may be possible they were driven outside of their limits due to the low sensivity of the speakers, the size of the rooms and the SPL level. They would sound bright if they could not cope with the current drawn by the speakers when trying to reproduce a lot of low frequencies. The same could happen to any AVR if they are push beyond their limits.