Definitely a good thread to look at since he used a billion different parts on his build. Too bad he disappeared off the face of the earth.
I will affirm operadude, the cossie makes power higher up in the powerband and on big turbo's. Down low you'll suffer, and on a small turbo you'll suffer. Both of those and you're really hurting a stock turbo set up.
The cossie tgv's sound like a good idea. They're a composite like the stock IM so they really reduce the transfer of heat. They basically turn the whole tgv into a phenolic spacer, which is what the whole IM is too.
Looks aside, the newer manifold will perform at least as good if not better than any aluminum/cast manifold just because of the reduced intake temps. I can't comment on the particular flow characteristics to the WRX/STI manifolds that are aluminum, but I also don't see much difference between the two flow wise.
They're also sweet for going with a reverse intake manifold setup as long as you don't mind doing a rotated setup.