EGT's rarely over 500C at the down pipe, so 700 ish turbo. It's much the same as running a T34 on a YB ar 33psi, or a 500 T4 engine. You are according to theory out of the turbo's power range. However, in practise it works. I've has my own RST for 9 years, a daily driver untl last March, and it has never melted anything. 0.48's on 1600's are laggy - i know as i've got one and mapped lots. It's just not worth the sacrifices on a 200hp engine.
Antii, exhaust temps aren't worth worrying about once the car is mapped properly on a bar of boost. The std turbo will work at 15psi, but it's working hard, and it's life will be shortened. However, this is what the majority of chipped RST's are, and have been for 20 years. If you can spare the cash, go for a stage 2 turbo. A little more power, and it isn't spinning as fast. Will last too, Turbo Technics are comforable with theirs upto 22psi.