I have a 3 inch twin tip x-force varex on my CS4 with a 3 inch turbo back exhaust. Personally i am extremely happy with it, had it for about 6 and a half months and i would never go back! Doesn't piss the whole neighbourhood off in the morning
Got mine installed at Mettam's Mufflers in Belmont - Unit 4/135 Great Eastern Highway Belmont, 9479 4567
$600 bucks installed...little less for the cannon i think (just for the tip, already had the
TBE)
Absolutely great bunch of guys! i've actually been there a few times, and will continue going there for many years to come.
On the twin tip its not really noticable/visible that there is a butterfly valve...where-as on the cannon varex it is quite visible....seeing as they aren't exactly road legal (according to x-force) probably not a good thing....
If you really want i am more than happy to come and show you it/let you hear it etc...