Jpms, While I am sure that Mick can complete the modifications you've requested, I think you'll have better results with a stock unit. While many of the mods seem minor, they can impact the original design and impart negative side effects.
In all honesty, I would especially stay away from having Mick do XLR connectors on your preamp. The circuit was designed specifically for single ended operation not a balanced signal. Mick tried this on two of my preamps and the results were not good - at all. A local technician told me it would likely cost $500 to trace the problems and fix. Mick charged me $50 for the option, so.. I didn't feel it was fair to have the problem fixed at Micks expense. On my preamp, I have the wrong end (Mick used the Input connectors as the output) and connected some extra transformers for the balancing of the signal. This is the second preamp that *I* have had that he did this on. On the second one, he wanted to fix the problem but then made the same mistake. Oops. Using the XLR's causes my preamp to make huge loud noises when switched to XLR.
While I am rather pissed off about the XLR "issues" I have had, I think that Mick's design is one of the best in the world. The sound is spectacular from a well built unit and quite frankly will by itself transform a system.
Just settle for RCA. Its very good. While very snug and nice to use, balanced connectors are over-rated unless you're running VERY long lengths of cable. If your amplifier only has balanced inputs and is a "fully balanced" design you might want to think twice about attempting to use the Supratek SINGLE ENDED DESIGN with that amp. Even if the Supratek has XLR connections - that does not mean its a balanced signal. In this case, I think you would lose performance with a single ended preamp.
Biamping is possible with a stock Cortese or Syrah because they have two sets of outputs. I am sure Mick could put three without a glitch though.
The extra power supply connection on the preamp shouldn't be a problem but you might want to seriously re-think buying a Cortese line stage only. His phono is even better than the line stage and its a pain in the butt to have him upgrade. I'm going through this now myself.
When I originally purchased my preamp, I didn't think I'd get into vinyl. Now... I've tasted what it sounds like in a high end system and its so good that IMHO, you would be better off asking Mick to remove the line stage and just give you the PHONO - get rid of digital all together!! I am kidding of course but the extra 1,500 for the phono at time of purchase will save you $$$$ in the long run for shipping / duty fees, time, etc. Something to think about.
The TMC cables are a pain to deal with. They sound "okay" but not fantastic. They will save you a lot of money but are so stiff that it makes them difficult to work with. When you read about them being stiff and imagine something in your head based on your past experience with what you think to be stiff cables... take that thought, and then multiply that by two. They are that stiff... In fact, if I move them, they will push my Supratek right out of the rack and onto the floor.