He stated basically, the basic preamp internals would probably be identical to the AVR.Not likely, AVR's use some sort of an electronic/digital volume control, and stereo preamps generally use an analog VC.
If you need the AVR for HT, then use a stereo preamp/amp or integrated amp with
HT by-pass. For 2 channel only, I can't see any advantage to use an AVR.
You already have the answer to your question,
I know using an AVR as a pre with external power amps (pre outs) is not sonically the most ideal.