Superchargers are expensive, get test pipes, Intake, tune and use good gas you should see 40hp at the wheels.
I just did this with dynos and am happy w power. I have always wanted a SC but the intercooler versions are just out of my spare cash range. If you budget it correctly,
1. 585 sc is 11000 after all in
2. You need tires either more often on average so budget 2500 a year max for this
3. You'll need brakes budget 5000k in brake upgrades
That's a lot I dough even when not doing brakes and or tire upgrades
A used supercharger is pretty well priced at stage 1 however stage 2 still pricey ... And better to be safe than sorry with the intercooler option.... Even though results show stage 1 to have minimal heat problems / changes.
One day I'll have one