I have personally heard the Granite 650 in Stephen's home. Related components were Granite monoblocks(with KT88 output tubes), Sunfire preamp(HT, I believe), and Osborn Eclipse(I think) loudspeakers.
It was a very musical player. I would agree with the assessment that the sound can be characterized as warm and forgiving, as opposed to analytical and detailed. I give it about as high a grade as it gets. In my opinion, this is what most people who are searching for an analog sounding player are in the market for.
At the time, he informed me about the upcoming(657). Tube output, and what we believed would be upsampling to 24 bits(it is actually 20). The price turned out to be higher than I anticipated, although still cheaper some of the competition.
As I have not auditioned it, I am obviously not certain of the level of improvement the 657 offers. However, based on my experience with the 650, and the extra development put in by this fine company, I would expect big things. As it is, I definitely recommend either player.
I do believe that if the statement above regarding that they are basically the same player, with the 657 incorporating a tube output stage, it would increase my need to audition the two against each other. If this is in fact the case, a question of value would arise. To the best of my understanding(please correct me if I am wrong), if an external DAC(very common as the technology moves forward, as we all know) was employed, a tube output in this type of player is bypassed, possibly mitigating what the increased cost of the circuit offers. Of course, as in any audio purchase, a careful audition can never be replaced.
Back to my impressions... Unlike the Rega Planet/Planet 2000, the Granite does not slow down or thicken the sound. I have been been around the Electrocompaniet CD player a good bit, and listened to the Audio Aero Capitole at NY HiFi 2001. Both of these players also give the type of sound that we have all been hoping for from the digital medium. I put the Granite 650 in the same boat. No, I have never A/B'd any of these players, but all three could make it into my system any day.