I bought the Sony STR-DA6400ES. The short answer "it is amazing". I am still shocked at how good it sounds.
I have been listening to it in two channels stereo. Basically using it as an integrated amplifier with a built in DAC. I used it through its tos link with the Polk Audio Sirius receiver, coaxial digital with Theta and JVC transports. I used it through its analogue RCA input with Theta Gen VIIIa DAC and Audio Aero prestige SACD/CD player. Yes Satellite Radio can sound very good.
In all cases it sounded great. Competitive with $10k or + pre/power or integrated amplification. Its internal DAC is excellent.
It is smooth, fast, clear, detailed, transparent, musical, and engaging. Its sound stage is wide and deep.
It is amazing that it provides so many functions sound so good at this price. Check Michael Fremer review in Home Theater magazine and Sony web site for more details and specs.
Make no mistake about it this Sony STR-DA6400ES Receiver has a true Audiophile Hi End sound. Up there with the big names. I know it is hard to believe it but IMHO it is true. BTW I have no affiliation with any audio or video entity.