XA5400ES owners - what are you using now?

Having said that, depending on how  "high resolution" your system is, a top of the line Sony Blu ray player used as a transport and used with great coaxial cable (Cardas, Ensemble) and any good DAC will give these run for their money ....

The OP didn’t mention two issues 
1) Does he listen to SACDs? Does he need Blu Ray?2) Budget 

I use my Sony as a transport into a Bryston DAC3, which accepts HDMI.  For SACD, the DSD is outputted from the Sony.  If your budget can stretch that far, then you can use the Sony as a transport.  The Bryston has 4 HDMI inputs so you can add a cheap Sony Blu Ray if you wish, or you could sell the 5400 and just the the Blu Ray as your transport for all silver discs 
  

Yes I listen to SACD as well as CD, and want a unit whose internal DAC can be externally accessed for DSD streams. No need for Blu Ray as this is 2-channel audio only and I have none of those. Budget would cover any of the units I already mentioned (target $3-4k give or take - somewhere south of dCS gear ). I am ready to move the Sony on to a new owner.

very happy with the Yamaha CD-S2100, like it more than I expected to

I think this is a great time for you to think out side of the CD spinning box and go server, hard drive, or an all in one system like the blue sound vault (load your CD's and forget) and lose the CD spinners for good and stream from a hard drive you will never have to deal with a failed CD drive again. CD spinners are a dyeing format, I know there are many old folks here who are dedicated to them but in this day and age its just not necessary to get the same sound. 

Get your self something like the Blue Sound Vault2i load all your CD's and never have to deal with them again. Add a better DAC as needed and your set. there are other methods of losing the CD player but there has never been a better time to move on.