Just picked up a N/A Elise over the weekend. I wouldn't call the car fast... I know supercharging seems to be the method of more power here but I prefer a turbo car. I know have a shop make a full custom kit for a killer deal. The only question I have is how well do these motors hold up with appropriate boost and a solid tune?
I, too, prefer a turbo over a supercharger but they are A LOT more work on these cars. I'd recommend going with a FF kit (if you can find one) or a Radium kit. Just about everything else is going to require going custom, which obviously can become extremely expensive and can introduce a plethora of new complications. Avoid anything "Hass" like the plague.
You say you know a shop that can make a custom kit for a "killer deal". I've heard this literally dozens of times on here and it rarely ends up being the case. There are a lot of little eccentricities that these cars possess and custom kits almost always end up being huge nightmares.
300hp on the factory engine is doable but I wouldn't go much higher than that. I've heard numbers all over the place for what a non-tracked transmission can handle but from what most people say I think you should be OK with the power 8 psi or so would give you on factory compression. Might want to upgrade clutch, though.
2006 ST Exige - GT-28RS, Darton sleeved/decked/line-honed, ARP hardware, Wiseco 8.8:1 pistons, MWR valves/springs/retainers, RC injectors, Walbro pump, CWorx oil pump, Moroso oil pan, S111 TrackMounts, Spearco intercooler, GReddy catch-can, Turbosmart BOV, Fidanza clutch/flywheel CF Panels/scoops, S111 Rear Diffuser/Rear-Panel Delete/discNOIR Brakes w/SS lines/RTDbrace/Towhook, APR CF Splitter Alpine unit w/MBQuart, CF binnacle/shifter, Schroth harness, S111 shift brace (Sold)