The DSP will certainly enhance a stock motor with the canned 91 tune. Take a look at the link below for some real world, on the dyno, results and comparison between the stock and 91 octane tune:
The biggest difference is where the power comes on at a lower RPM and is sustained longer. Also, the air / fuel ratio dropped from a lean condition right into the sweet spot for the HEMI.
The beauty of the tool is the programming options. Once you start getting into some motor mods, those can be accounted for with a custom tune.
Sounds like you are going to get a CMR tune after the new exhaust is on. That will REALLY wake it up. I had my SRT done last year and whoa...what a difference! Don't get me wrong...the Predator on it's own is great!