The Volant install was pretty straight forward. A pretty basic bolt-on application.
What i liked about the volant was... yes, the power gain, but also that it was still recognizable under throttle. With the volant air box, you can easily create an opening in the front of the box, increasing air flow (in theory) and "growl."
It is definitely no substitute for an exhaust, though.
sparktite-
You can pick up a CTS-V exhaust from a V-owner in your area for as little as 100 bucks. No performance gain, but cheap way of getting a note out of the car.
Or go custom. Check out the thread made by "SVB4EVA" called, "Finally Broke Down... Custom Exhaust!" or something like that. I think he spent less than 500 bucks for his whole system and, having driven behind for 50+ miles, I can vouch that it sounds great. (More noticeable than the magnaflow on my 5.7)
there are a couple more options.
Check out
www.cadillacfaq.com >> "videos" for exhaust clips for your car.