x pipes are deffinatly the way to go. as for losing power, or gaining power for that matter, i dont think you'll notice it much, down low anyways, but past 3000, you'll feel it deffinatly. there is one guy i know with the upr x, and it dose sound nice. its deeper then my bbk x, but mine is WAY louder. i dont think he has a after market cat back tho, i think its just some flows welded in to stock tailpipes. i love my bbk tho. i have people asking all the time now what my exhaust is. and i get alot of responses that go something like "really, i thought that combo was suppoosed to sound lik poo.".
id get the upr one tho, it is kinda nice with the 2 peice designe. just make sure its tight, you dont want a leak.