Denon AVR4306 vs. Sony STR-DA7100ES?

You should toss in a $225 unit while you are at it, the Panasonic SA-XR55. It'll match those two units for power output and THD. It just won't have as much connectivity (then again, few people ever maximize all those inputs).

Sony uses their own proprietary switching technology on their ES digital amps. It's not quite as good as what the competitors use (Class-T, Equibit, Ti), so distortion would probably be a bit worse than the Panasonic or Denon (which is still an old school analog amplifer). On the flip side it does have more brute force power than the Denon or the Panny, but most people rarely use more than 25-30 watts continuous anyway during playback.