I've just put an EternalCar system on mine. 120 quid delivered for the two centre sections and back box.
It looks to be the same quality as the GM systems currently being supplied, going on the pictures from Chrisgixxer.
Eternal don't list an exhaust for the 2.6 / 3.2 facelift but I can confirm that the 3.0 system fits except that the tail pipes on the back box don't extend quite as far as the original. They also don't have the chromed trims on the end, so I will probably weld the chrome trims from my old exhaust onto the new back box, if they clean up OK, or go heavily disguised to the chavtastic section of my local Halfords and buy some new chrome trims.

Sound wise, it's difficult to tell after driving around with no back box for a couple of weels. It's probably a little louder than the OEM system but not in an unpleasant way. There's a very deep burble that probably wasn't there before but there's none of the irritating rasp that normally issues from a cheap exhaust. For the money I'm very happy with it indeed.
An Eternal system or a Stainless system are the only two options worthy of consideration, I'd say.
Kevin