Do some research on the turbo boost levels. Your question about the boost controllers, however, is an opinion. Buy a manual boost controller and save the ~$500 from the gizmo-tronic boost controller, IMHO. It has lots of blinky lights and pointless graphics, IMHO, but a certain crowd seems to approve of that sort of thing. Nothing beats a mechanical boost gauge or a high speed stepper boost gauge, so you can see pulsations, etc in the signal. The Blitz LED setup won't give you (or rather your tuner) the highest degree of feedback on what's going on.
I used to operate a speed shop specializing in turbo imports, so I've used most of the EBC's sold over the last 10 yrs. If you gotta have an EBC, I'd recommend the GReddy Profec-B.
If you want an opinion to reinforce the Blitz choice, go check out zilvia.net, nicoclub.com, etc. There are a million SR20DET cars on there that have already answered these questions many times.