GT4HUTCH

to my knowledge, the Roushcharger is THE only roots style blower for an S197. All of the other positive displacement superchargers are twinscrews. The magnacharger is a roots hybrid(kind of a cross between a roots and twin screw in terms of rotor design). Roots tend to be a little less effecient then twin screws.
I personally would sacrifice the extra top end horsepower of a centri for the instant low end of a positive displacement anyday! It just makes for a car that is more fun to drive. IMO

mygt500

I agree 100% on all points GT4HUTCH!! ^^^^^

cobra443

Whipple FTW! haha IMO here is the rundown:

Twin Screw : Centri

Whipple : Paxton
Saleen (very very close second) : Procharger
Kenne Bell : Vortech

S281 E

Once you determine what type of blower you want than you need to figure out how much power you want from it. Than we can really narrow down your options.