Kind of a loaded question. I'm also planning to supercharge my own 99 SLE. I've already got the parts, too. One huge issue is the transmission, which likely won't hold up for 40K more miles with my current mods. A Kenne Bell supercharger is a big deal. Its cost is huge, and you really shouldn't put it on your car in its stock form. A Series III is a different kind of engine than what you would have with a Whipple and 9.5:1 pistons. Are you just surveying basic options? I think it would be cheaper to go with a lower intake manifold from a Series III engine and also to get the supercharger, L67 throttle body, L67 to Gen 5 TB adapter, L67 fuel rails, heads, and an SS M90 pulley. That would be a relatively cheap way to go supercharged. A Kenne Bell supercharger is a whole new game, but it would be cool to see you try it out.
94 STEi and 99 SLO