There is no parasitic loss through a turbo but I still wouldn't push more than 7-8psi on a stock engine. If you're rebuilding this winter (and turning up the boost I'm guessing), just wait until then to change setups and set up the car for max desired boost. Then get it tuned once so you're not having to pay twice in one year for tunes. Have Lito work up the base tune while the car is coming apart so when it's put together you will be ready to start the car and do logs for final revisions.
As for selling the M90 setup, I think you can do better than 2k since you're including headers, intercooler & pump but again it's up to you.