Love my CPE. It does drone some between 2700-3000 rpms but only with a load. Otherwise, it's loud and sounds awesome. My buddy wants to sell his Cobb system and get a CPE after hearing mine.
I don't even notice any 'buzziness' any more on my CP-E Nexus system, but due to fear of LSPI I am also obsessive about never even getting close to lugging the engine at all, ever.
I know you are speaking to throttle application/load under normal, and not lugging conditions, but I don't even sense that 'drone' any more, and I have a fully gutted interior behind the front seats, all of the time.
Either I am losing even more of my little bit of hearing left, or somehow I have become 'habituated' to the noise.
The Thermal does look 'prettier' under the car, and does not have the funky 'branched' Helmholtz chamber up into the back bumper area, but I would
never switch to that system just because of any sound differences.