You guys are forgetting....
The supercharger kit that is now available for the SL. According to Geoff, you get similar gains that you get on the SOHC (about 70 hp and torque. That makes the SL jump to 292HP, and 275 ft/lbs torque, at about 500 lbs less. You'll never get a VR-4 off the line (what can?) but damn if you won't walk a stock one from a roll. And that's set at a conservative 5psi. The kit costs $4k, though I higly reccomend a hard pipe kit, BOV, intake, exhaust, and AFC. So total, you're looking at 5500-6k on top, if you do most of the installs yourself (excluding exhaust). And it doesn't have to be all done at the same time, so whenever your budget allows, you can do things one step at a time.