On my car the gt500s were never deep, they were a bit boring and tinny. I'd love to hear them with the cat deletes though. The maxflows were very deep. Without cat deletes I can say that to my ears they were the perfect setup with the lethal x pipe. If you look at the first video, that was with...
I believe Jones supplies Summit with thier "Summit" brand mufflers.
Here is the 3" offset/offset MAX Flow under the Summit name. Still a great value at $39.97 a muffler.
https://www.summitracing.com/parts/sum-633002/overview/
I had the same issues with the first version kit and the newest design is different, using your OEM maf for tune only kits. I have no driveability issues with the newest version that is now being sold.