this is my 35th with the vortech installed i was one of the first to install this system. belive me i had some problems.

 

looks good.....how does this system compare with the stillen sc?

 

that looks like a way better belt setup than the standard 287 hp engine vortech

 

The two systems are about as far away from each other as any two forced induction kits for the VQ35 as can be. The Stillen is a nice instant throttle response feel, which makes great use of its very limited power gain. The power curve seems to peak early and stay pretty stable.
The Vortech has a good bit of lag before spooling up (around 4-5K rpm's) and then it will unleash its power untill redline. There seems to be only about 2-3K rpm of usable power there, and it is all on the top end. The Vortech will make more power than any stillen will, but the Stillen makes better use of it. IMO, and I have both.
Both are a decent FI kit, both have there pro's and cons. It all depends what your goals and driving style's are like.

 

the stock vortech out of the box is pretty weak

I'd upgrade the pulley to the 3.12 pulley at a minimum. If you run shorter gearing like the 3.9 or 3.7 final drive, you'll be higher up in the powerband where there's more boost being made, and the gear multiplication will be higher so you'll get a much better kick in the pants feel.