Which Sony: SCD-1, XA777ES or XA9000ES?

I think the SCD 1 is very good.

The SCD-1. Take a look at Audio Asylum on this, there are a lot of posts on this topic on the Hi-Rez Highway forum. The big difference is the transport, which was a cost-no-object job on the SCD-1 and, according to the posts I recall, a much better unit than the subsequent models. Sony pulled out the stops for its initial flagship, has not improved on it yet for two-channel playback, concentrating more on multichannel and cheaper mass-market models.

I have heard all three of these players in my system. There's no doubt that the SCD-1 is better built. The problem is that better sound is in the ears of the beholder and the term best might not sound the best to you.
I favored the xa777es over the others personally. I found its slight softning of transients to work better with the myriad of crappy cd's out there. I think the SCD-1 is better in absolute audiophile terms but I personally think the xa777es is more musical with about 90%+ of the stuff out there. It is on par with about anything in SACD playback
I have been very satisfied with mine. I honestly liked it better than the SCD-1 and it sure initializes disks faster.
I didn't like the xa9000es quite as much as the other two even though its construction is almost an exact copy of its predecessor. It doesn't sound quite as pristine---but here again, that's me.