Welcome to Just Commodores, a site specifically designed for all people who share the same passion as yourself.
IMO, a single 2 1/2" sounds terrible on the VZ V6's. Some like them, but most don't.
I do a twin 2 1/4" into single 3" that sounds a lot better, nice and deep with no drone. Has a moderate bark when you get up it, but it doesn't sound like a Skyline. $495 shipped Australia wide.
(Shameless plug, and post number 12 000, yay)
what engine do you have? i know the redback exhausts sound really good on ecotecs