The 2 piece that comes with the arctic as standard is something else, constant pops and bangs, real head turner! I had a Cooper S before the VXR and never really rated the S/C but I think going from the VXR 1.6T to a 2.0 NA it just feels like I'm missing something, your right when you say the power at the top of the rev range is great but sadly I don't drive above 4500rpm wherever I go ha!
I personally would switch back to an arctic in a heartbeat. Yet to drive the new Fez ST but heard many good reviews about it, may go for a test drive if you think its worth it?