I thought you had noise with 2 NADs? Why would you want to try 3rd NAD?
All these numbers - even THD of 0.015% -- are inaudible.
If you're talking about NOISE from speakers, that's SNR (signal-to-noise ratio). That's different.
We will see what the SNR of the CX-A5200 is when Gene posts his review, but the SNR of the CX-A5100 is about 131dBA!
Also keep in mind that most speakers have a lot WORSE noise and THD than any pre-pros and even $300 AVRs!!!
Again, all these numbers are inaudible. I would focus on the price, features, aesthetics, etc.
Sound & Vision Magazine
Yamaha CX5100: SNR 130.92 dBA, XT 94.21 dB
Marantz AV8802: SNR 130.38dBA, XT 93.16dB
Krell Foundation: SNR 128.33dBA, XT 100.61dB
Anthem AVM-60: SNR 127.91dBA, XT 107.90dB
Integra DHC 60.5: SNR 127.11dBA, XT 95.18dB
Classe CT SSP: SNR 122.13dBA, XT 102.93dB
Bryston SP3: SNR 121.59dBA, XT 93.44dB
Cary Audio 12: SNR 121.03dBA, XT 93.41dB
Lexicon MC-8: SNR 120.18dBA, XT 92.64dB
AudioControl M9: SNR 118.63dBA, XT 91.55dB
Denon AVP-A1HD: SNR 114.57dBA, XT 111.95dB
Anthem D2: SNR 113.13dBA, XT 112.97dB
NAD M15: SNR 112.67dBA, XT 109.73dB
Rotel RAP-1580: SNR 99.04dBA, XT 86.1dB