That's what I thought as well. I had the AT-300 clone - IOTAVX AVX17 in my living room for few days. I did not use any room correction. Simple bass management to route 80hz and below to 2 subwoofers. Room correction was done & stored in my Genelec speakers.
Subjectively, the sound from IOTAVX was very good for movies but though decent it was a bit flat for 2 channel music in straight mode. Auto umpixing (assume Dolby Surround) for 2 channel was better than straight mode. Because of the delay in HDMI hand shake, lack of bass level adjustments without touching eq, I went with my next option Yamaha CX-A5200.
With the same settings in Yamaha as in IOTAVXi.e. no eq, no room adjustments, same volume levels, same distance - to my ears 5200 sounded different. More clarity, smooth, airy and sound was more engaging in YAMAHA compared to IOTAVX. Not that I was not happy with sound of IOTAVX but it it definitely different. I would say IOTAVX in 2channel was bit flat and harsh whereas Yamaha was engaging.
I feel that the DACs along with the implementation made the difference in sound. ESS 9026 Pro vs Cirrus Logic CS42528.