As many have already mentioned, there really is no substantial power to be gained from an axel-back muffler. Most of the power to be freed from the exhaust would be by deleting the primary cats.
There is some very educational information in this thread regarding Evolve's new E-Tronic Valve Exhaust. They actually shared data testing looking at different parameters such as back pressure, power, torque, and different valve settings.
You also mentioned the Dinan tune. I would highly recommend you look into other options there that offer a lot for their value.
If you are looking for power, while keeping costs down, I would personally get the Evolve XPipe and Tune.
If you are looking for power, refined and adjustable volume/tone, with no limit on costs, I would check out the Evolve E-Tronic Exhaust and Tune.
My biggest recommendation is that you try to find cars that have different exhaust setups and listen to them in person. Videos and Audio clips can only depict so much and often times, they're never entirely accurate.