I think you should install both!

Stage them correctly and you can have the supercharger for getting up to speed, and then the turbo for top end without any supercharger robbing power! If you wanted to be really trick you'd put in a switch and clutch so you could disable the supercharger entirely.

Just did a little math, the way I see it this setup will require at LEAST 6 blow-off valves, with one after the muffler being mandatory.

You're right about the tuning, supercharger boost is read entirely different than turbo boost when it's going into the engine. You could get one of those sweet power programming chips off e-bay though.