Speak to MA developments.
I am looking for around 400/400 myself. I am told this can be done on standard manifold with a full 3" exhaust system, induction kit, 255L fuel pump and a re-map.
So I suggest this is a good starting point.
If you looking for 400+ then that's where the big bucks start to kick in;
uprated turbo, rod, pistons, injectors, quality tubualr manifold etc.
Speak to MA developments, tell them what you are aiming for and they will put a proposition your way.
In short though you should be able to get to 400bhp or very close on standard turbo and internals.
As for Elbow, I have been looking into this too. It's just a question of what comes with the DP, either mated to the original elbow or an uprated one included. I think it is a little restrictive but ask MA what they recommend.
When I get round to doing mine I'll let you know what was suggested to me.
Good luck and keep us posted on the upgrades