Is a T3/T04B a good upgrade for the SR20? If not, what is?

If I were you, I'd upgrade with a kit for the SR, like from Blitz, HKS or Apex'i. I've heard that Apex'i's RX-6 turbo upgrade is super badass and Blitz's upgrade kit is some of the best quality out there.

Ok, but what I am saying is that, if I turbo my KA, and in the end decide that I want an SR (which I probably won't, but its possible), I want to know which size turbo I could buy to boost my KA, and then install it on an SR for an upgrade later on.