Don't forget to look at the akrapovic's. They seem to be of the better quality.
I heard the laser, the devils and the leovince's in person. Leovince sounds best, no doubt about that. The leo's sound very deep and very warm. And once you open the trottle they scream like hell.(they all do that offcourse)
The devils are also very deep, but they seem to sound less pure and warm, more side-sounds are heard. And with side-sounds I mean sounds that don't match the main deep sound. It seems just less smooth.
And the lasers are more quiet and don't sound really deep. They sound more in the line of the stock exhaust.