If your looking for a single box with a lot of power then you'd be better off looking elsewhere. The Banks Six Gun by itself simply isn't that impressive when it comes to power. After all, it's simply a high end pressure box w/timing as the Dodge application adds no duration.
The PowerPDA is what really sets it apart. It's a great monitoring tool with audible alarms and comprehensive set of gauges. It also allows you to customize each level with different parameters. My favorite parameter is the "Accelerator Pump" as you can use it to help keep down the smoke in day to day traffic or increase it to help turbo spool.
As for stacking I'm currently running it with a Superchips FlashPaq, and it's working great. However, as soon as the Smarty comes out for the '06 I'm dumping the Flashpaq.
Would I buy the Six Gun/PowerPDA again? Yes, I love the PowerPDA and smooth power and so far stacks great with downloaders. I'm also getting 21MPG with my combo so I can't complain. But if I could only purchase one thing it would be the Smarty.
Thanks!