I run Cass's Stage 4 brake kit currently.
In terms of total piston area, I believe the current calipers he offers in this kit would be similar to the 4-piston GEN II Viper calipers. The calipers Cass provides use an 03+ GEN III Viper brake pad already.
So, what am I missing here other than the (possibly) lighter, two-piece rotors? Just the ability to use the authentic Viper calipers?
Cass will have to answer that. From what I understand there might be a supply issue getting the knockoff caliper. The OEM design should be around for a long time since Vipers will be around for a long time. Downside is cost of course.