To me, it sounds like an overpriced stock exhaust system with a restriction at the mufflers where it necks down to 2 inches. I'd go with an aftermarket system (Mac, Flowmaster, Borla, etc) over the FRPP one in a heartbeat. They may cost a little more, but it's better than replacing stock parts with essentially stock parts again.
That's what I'm planning as well. Currently running Flowmasters, but I want to be obnoxiously loud at WOT. Spintech Pro-Streets should help me accomplish that with no problem