If you step up to any clutch above stock and beat your car, the trans IS going to die. I have been through 3 T-5 's now and have had stock, centerforce and a FMS clutch. The FMS clutch and the Centerforce seemed to grab the same to me ( maybe thats because they are both made by valeo) but i wouldnt blame either performance clutch for the destruction of the trans' they were hooked to. if you plan on adding any signifigant amount of power later on, dont waste money with the T-5 setup cause most of that stuff wont work when you go to switch to a tremec.
I just put a TKO in my car with a FMS puck and a Centerforce pressure plate.
Spec Stg 1 here with a t5. The spec is on its 3rd t5 (they were all crappy ones laying around besdies my current t5) and still hasnt missed a beat, i launched on nitrous wot with et drags and dead hooked everytime. I think itsa great combo no need for anymore clutch on a t5 and any less for me wont last long.
The king cobra is def a good clutch. Pedal effort shouldn't really be much if any worse than stock. the frpp heavy duty is the exact same clutch, same holding power, just a much stiffer pedal feel. Most would hate it. I don't know about using the King cobra on a 300 hp car though. It's kind of a boring clutch. it's good enough to not slip, but soft enough to where shifts are boring and it doesn't slam like a spec will. However, that's probably a good thing for the t5. I wouldn't touch the stage one specs, or the stage 3's. Stage ones are very prone to chatter. From what I hear, the stage 2's are not as chatter prone, but I only have experience with the stage 1, so I can't verify that.
I'd personally recommend the centerforce dual friction. It will grab hard, but not as brutal as the spec, and it will hold more power than the kc clutch. I love my bro's centerforce clutch, pedal effort is lighter than stock, and it grabs great and hard, but not too hard.