LS6 intake manifold

Yeah I’m looking into simply bolt on options for this LS1 in the GTR. LS6 intake manifold was on that list. I’m up in the air as whether I want to buy a ~$300 ls6 manifold, or have Don spring for more money and buy something else. I’d like to get this car somewhere in the 375-400whp range if possible with bolt-ons/cam/heads/tune etc…