Whatever you do, do not go QA1. I have one and I had to bore out the 4 mounting holes, to allow enough adjustment to get the piece of shit to align right. The QA1 also pushes the wheels out a 1/2". I've heard good about the UPR, supposedly it's the lightest one too, If I could do it over again, I'd go with the whole UPR Kit (K, A-arms, Coilovers).
Also I wouldn't recommend the UPR or Qa1 for anything but drag/normal street use. Since I install mine I don't take turns and corners nearly as fast as with the stock K. Road coursing and hard cornering I'd only trust MM or the higher level K's.
Toy - 01' Bullitt #3320: Borg Warner S475/83 - Built 4r70w
DD - 09' Kawasaki ZX6r