From the reviews I read about the CD8X, it sounds like the PSX-R is a worthwhile addition, but I'd be very surprised if it made your problem go away.

I feel the same about the MF tube buffer. I would expect no more than a small improvement in most systems.

I would first experiment with a few decent cables. You can probably borrow a few from your dealer to test them for a few days. You might be surprised at the difference a good cable can make over a bad one. Same thing about loudspeaker cable BTW.

If you could also borrow some other CD players to test in your system, that would of course be best. I have a Njoe Tjoeb CD player with a valve output stage and it sounds wonderful - magic midrange, no harshness, cost me only

If you have a high end shop that will let you try a few cables at home as demos, you might consider using a really fat speaker cable before giving up on the cyrus. Running a 9 gauge cable as full range as opposed to biwiring could be a good start to see if you can tame the tonal balance a bit.

I can say from experience that the Tara Labs Reference Generation II interconnect will roll-off the top and take a pretty healthy dose of the edge off and add weight down low.

I've heard the Cyrus stuff and as a house sound, I found them very lively and a bit thin. The optional power supplies would increase the spread and definition considerably, but thin liveliness remained. I would think that this gear would partner better with warm sounding speakers.

Changing cables in an effort to mimic tone controls is in my view an unattainable goal. Fine tuning yes, but if you have a basic glassy sound then stronger remedies are needed. I had some success with the first version (X10-D) of the MF tube buffer, but whether this will work with your combination of a bright cdp and Naim amplification is another matter.

If you end up replacing the cdp you should consider something that up-samples - my Arcam CD93 gets closer to analogue sound than anything else I know at the price.