Hello,
For what its worth I bought a fully decked out CDD John himself had been using for a year or two. It had a recently replaced CD mechanism (one of the very last he kept privately) and John told me he would just add stuff to the transport over the months. I can't compare a modded CDD vs non...but I can tell you I'm very happy with my digital.
I would also recommend a MJ digital coxial, I happen to also use one of Moray's PC's on my Bitstream (heavily modded) DAC as well. Although I actually prefer my Blue Circle PC. The most stunning tweak I've run into so far is a Skylan isolation system which is little more then two slabs of wood with some voodoo magic substance in the middle and some ceramic feet. I say voodoo half kiddingly cuz I'll be damned it actually worked. I didn't think it worked when i bought it because I had the system setup wrong; I had the transport resting on the feet and then the feet on the platter, it was only a year later somebody looked at my system who also had a skylan stand and said "you might actually hear results if you set it up properly" I was pretty suprised when I did the switch; it somewhat renewed my faith in this tweaking nonsense.
If you don't use isolation it's fairly cheap if memory serves it was like $200-300, its an operation out of Calgary (John's home town). If you're into Jazz a Bitstream DAC might be all that you will ever need. It's about as analog as I've ever heard.