GST's prices are that great on the ACT bits. I found the 4-puck elsewhere for $100 cheaper than the 6-puck.
As far as rebuilding the hypersingle: it's near impossible to find anyone that will sell you the bits to rebuild it, and it would end up costing me hundreds of dollars anyway... like $500 for a puck disk I've heard. They hypersingle is proprietary, the flywheel and clutch are specific to each other. So, not much I can salvage out of that setup... which is why I'd like to go to the ACT stuff... if I kill the 4-puck, I can swap in the 6-puck, or the street setup, or pretty much whatever... hell, I can even put stock bits in there if necessary.
I found both the 4-puck clutch kit (SB4-HDR4) and ProLite FW (ACT-600240) here, for about $800 not including shipping:
http://www.mach1car.com but I don't know anything about them.
With regards to 4-puck vs. 6-puck... they hold the same power, the 6-puck is a little more streetable and handles higher temperatures, but the 4-puck is lighter and most places seem to sell it for just a little less. Since my car is never on the street, I'm not worried about driveability. Plus, I don't think my clutch sees all that much heat... I'm not launching it... at least when I'm not pissed off leaving the pits trying to get a clear track. So, I think I'd rather save $20 and gain the faster response of the 4-puck.
But, after pulling the car off the trailer and taking it for a lap around the block... I'm not 100% the hypersingle is dead. I'm sure I glazed the crap out of it, but it seems to be coming back a bit. I'm probably just going to bleed the pedal, and see if the catch point goes back to where it's supposed to be.