With $1600 you can definitely get a set of Enkei PF01's as I have a set of two 18x10.5s that I use as rain wheels/ spare tires. I think I got them for $325 each and I beat on these wheels before getting my track wheels.

I would definitly use the PF01 at the track as there are R35's that use them and the Nissan GTR is a fat pig

I agree that forged wheels are not needed, but neither is a cheap cast wheel that will be more likely to fail at the track