For 6-8psi you won't need a intercooler and for that sort of boost a T03 will do.
I am building a new engine for my turbo setup. I am running a T04e at 14psi with an intercooler (can run up to 30psi), low comp pistons at 8.2, and my engineer said it will get about 175rwkw, so I am not sure who told you that. I am spending big $$$$ on my setup, but you can do a lower boost setup on the cheep. If you want the 300kw (200rwkw) then pack a big wallet.
200kw at the flywheel now that is acheavable no probs, just keep in mind that you may have to decompress the engine if you plan to run 8psi. this can be done with low comp pistons or a decompression plate, it is just like an eatra head gasket. The first is the better method. You may also need a custom cam, a ecu I am using a heltech in mine.
check this site for a bit more info www.capa.com.au
I hope some of this helped