I've used a CDS1/CDSPS, a CDS2/CDSPS, CDS2/XPS, CDS2/XPS2, CDS3/XPS2 and would have to say that the CDS1/CDSPS has overall the best sound with a slightly dark but very colorful (and maybe a tad colored) sound. But the way its projects is unmatched. I also preferred the CDSPS to the XPS, the latter of which had a cool and bright tinge. The CDS3 (until it received some hefty mods) was pleasant but quite languid.
For 700 UKP in full working order snap it up. The black Burndy on the CDS1 is far far better than the gray one.
And yes, I have also compared directly the CDS1 with a CDX (leagues behind) and an early Linn CD12. Unfortunately my CDS1 was in the early stages of transport failure and was not sounding representative, but still was preferred to the CD12. For months before the transport did totaly fail, the CDS1 sounded abysmal with a hard, pinched and very compressed sound. So do have a listen to it before you buy. If it sound anything less that quite special, then something may be wrong. But the transport is robust and can be serviced instead of binned, something that I didn't have done.
I would say the CDS1 is the equivalent of the NAC12. Although replaced by bigger, better and far more expensive models it had a unique balance of tone and musicality that may seem lacking in later models.