What are TCXO and Superclock?

I don't think thats correct. You may want to research Jitter. From what I have read a CD will spin at a slighly slower or faster rate goverened by the amount of timing error.

A TCCO/TCXO clock being very precise, minimizes these variations of the transport/mechanism slowing and speeding up. This variation in timing speed may very well be Jitter. Don't know haven't researched Jitter myself.

Like I stated before Wadia, Gryphon, Gamut as well as Mark Levinson use TCCO clocks. These are all Megabuck players and I'm sure there are some advantages in using a temperature control clock vs. a non temperature control clock or they wouldn't bother with the expense.

Go to their websites and you will find some info on TCCO/TCXO clocks. Do a google search. Most of the info I was able to find on temperature control clocks was on non audio sites.

I plan to mod my Marantz SA-14 v2 CD/SACD player and has two options: use a TCXO (available locally) or a Superclock (need to import).
If I understand Audioengr's point correctly, because TCXO has minimal/no circuit to minimize jitter, Superclock is a better choice to improve CD playback performance? I read that some superclocks use TCXO for the timing part.

My Eastsound CDP has a TCCO as standard. A importer borrowed mine and was really suprised that it was a all SS design. He was very suprised there weren't any tubes in the unit.

How much the TCCO contributes to the "analog/tube" sound I'm not sure. What I did find out reading on line was that a TCCO theoretically can cut timing errors to 1/20th of a non TCCO unit. How this works out in practice and the advantages in real life, as stated not really sure. I do know several CDP's above $4000 use the TCCO. Wadia, Gryphon and Gamut being among those

BW Maxx

TCXO is a temperature controlled oscillator. The advantage is that the frequency tolerance is very tight.

Superclock is a module oscillator that has circuitry to minimize jitter in the output signal. It may drift and change frequency more than the TXCO, but absolute frequency is not that important in audio. The jitter is more important because the S/PDIF interface is affected by jitter.