I had the regular Xzillaraider and loved it. Craving more, I upgraded to the race version. Craving even more, I'm going to order the TST w/ the original twins flash.
I love the Quad modules due to their excellent performance, no CEL's or codes, and super easy quick installation.
TST is still the king of boxes, and installation is difficult the first time around. Additionally you'll be throwing codes from time to time depending on how you drive.
You'd better plan on an ATS, DTT, or Suncoast transmission, too. (Or a killer clutch, in my case)
I don't regret the way I went about it, but if you like to buy once, get the TST. You won't need to upgrade later. (well, at least not your box)