Depends on what you want. The centri type superchargers (Paxton, Procharger,
Vortech) are great for high rpm, but you won't notice much below 3000 rpm. Their boost is a function of rpm. The positive displacement superchargers like KB,
Whipple, Roush, Saleen, Magnacharger, have full boost throughout the rpm range--as low as 2000 rpm.
At the track, the centri's are just as fast (or faster) because you don't need the low rpm range that they are lacking. You're motor will probably live longer too, since you won't be driving around under boost as much.
For fun around town, I'd rather have the roots or twin screw, but you pay more for it. I plan on trying to find a good deal on one of these. Twin screws are technically more efficient, but for me it doesn't matter that much. Price matters more, so I'll include a magnacharger in the selection. These types are harder on your engine too, because of the low rpm power/torque.
That tuner kit that you linked to doesn't include everything you need. You'll still need injectors, fuel pump, tuning, etc. Count on a minimum of 4k for a complete, cheap centri kit, and 5k for a cheap twin screw/roots--non intercooled, add $1000 for intercooler or $400 for water/methanol injection.
