Well seeing as the single turbo is making about 428rewhp on a DynoDynamics (506rwhp on a DynoJet) at a little over 1 bar... a TT setup could make a good deal of HP...on an SRT6 motor, can't say for an N/A motor.

The problem you run into is a space constraint, seeing as I am not a huge of remote mounts (though I will admit there are quite a few amazingly fast cars with remote mounted TT setups). There are several other factors you have to take into account if going for a TT setup, the other biggest one I can think of being reaching torque limits controlled by the TCU, which there is only one person I know of that has hit that on a M112 engine.