I would think that the SA-11S3 would represent a worthwhile upgrade. Marantz CDP's tend to be on the warmer, more musical side of the fence. If you are seeking more resolution, you may want to look at an Esoteric K-07X.
One other consideration is possibly upgrading the Sony. I know Dan Wright of Modwright does some great mods with Sony players, like his Ultimate Truth mod. The question is how old is the CDP, and is it worth it to sink a couple grand into a 10 year old model? Maybe not a wise decision, but something to consider if you feel it still operates flawlessly..
One other consideration is possibly upgrading the Sony. I know Dan Wright of Modwright does some great mods with Sony players, like his Ultimate Truth mod. The question is how old is the CDP, and is it worth it to sink a couple grand into a 10 year old model? Maybe not a wise decision, but something to consider if you feel it still operates flawlessly..