about 3 years ago I had the CDS3 w/XPS hooked into a 250, 252. I then was able to acquire CD555 w/ 2 555DR'd PSU. At that time I had never before seen or heard the CD555. I bought the 555 pieces used from a dealer for around $15k, a fantastic opportunity, I believed. I was nervous about whether the new player would be substantially better than my CDS3, which I thought was great. When I received the new gear I hooked it up and kept the CDS3 connected as well so that I could do an A/B comparison.
I placed a copy of Hotel California in each player and pressed play simultaneously on each. As I listened to the CDS3, I got a bit nervous because it sounded very good. About 30 seconds into the cut I switched to the 555. It took no more than 3 seconds to have an OMG moment! That's all it took to alleviate any and all concerns I had about the upgrade being worthwhile.
Now, to be fair, besides the difference in transports, the power supplies were not the same - an XPS for the CDS3 and two 555's for the CD555. That being said, the 555 came much closer to sounding like vinyl than I thought any CD player ever could. I have since upgraded the rest of my system to a 500 amp and 552 pre, both DR'd. Those upgrades proved, even further, just how fantastic the 555 is.
This is a very long answer to your question, but I hope it helps.
BTW, I just arranged to upgrade from the 500/552 to a Statement. It should arrive in about 2 or 3 weeks. Obviously, I cannot wait to hear it!