you could probably save yourself some coin and use the standard GTR manifolds they work fine, i currently run the garret equivalent to the GTSS, the -9s, and they work great with the standards manifolds.
Big dump pipes go HPI they are awesome and i believe the Midori dump pipes and front pipe are pretty massive too
If you want response they are the turbos you want, listen to beer baron he speaks the goods
But good luck and hopefully you get what you are after!!!