Horse Power is a measurement for work done overtime, it is not what make the clutch slips.
TORQUE is the force that makes clutch slip, measured in foot pound or newton meter.
With an assumed 15% drivetrain lost, the clutch is seeing over 290 ft lb of torque. So yeah, not surprising a stock clutch will slip.
There are two vendors here that sells clutch, TU and FWD/Spec
If you want to be adventurous, there is the
eBay clutch you can try. No, there is no feedback on them. You'll be the first to try.
As for sprung and unsprung clutch, unless it is a factory clutch, I will only use unspring clutch. I had a sprung clutch failure, although the products design has been updated, I will not try it again. Other people also have sprung clutch failure, if you search you will see.
As for clutch material, Kevlar has lower friction but it has the longer life while Ceramic grabs better but life is shorter. Feramic will grab hard but wear itself out in 5000 miles so
it is a race only clutch.
http://www.phoenixfriction.com/t-clu...explained.aspx
Have you been to the TU website at all? Each clutch tells you what they are rated for.
http://turbosunleashed.com/shop/perf...35_97_163.html
TU clutch's pressure plate have the pivot points moved, so very little effort is needed to move the clutch pedal. I'm not sure about the spec plates.
If you want long lasting clutch and don't plan to even upgrade the power nor drag race, I'd choose yellow plate and Kevlar. Kevlar can not withstand HEAT, if you ever over heat the clutch, the clutch will be toasted. If you drag race one in a while, get the ceramic clutch. I'll leave the sprung and unsprung up to you.
Also, please note brake pads uses the same material as clutch disc, though you will not find Kevlar nor Feramic...