I have a set with the upgraded spring option.. I run them with the stock cam and a ported/extrude honed gt40 intake. They definately woke the car up pretty well, I hang right with a bunch of h/c/i combos in the area, but my car is also stripped, no hvac system/radio/console/rear seats, etc.. No dyno or track #'s yet, I'm still fine tuning the combo.
I bought them used for $400.. I'm not sure I would have paid $800 for them new, for that price you can score a set of used (or new) aluminum heads, shave a bunch of weight off the front, and probably make more peak power.