I have owned a radiator shop for 10 yrs. The extra 1/4 in of radiator core really doesn't make much of a difference. Are you having cooling issues? If not, I would go with a nice Koyo aftermarket Z radiator. They make a nice product at a reasonable price. They also have a lifetime warranty. I have personally had one in my 92 TT for yrs. in South Florida. If you are having cooling issues, I would investigate the reason and fix the problem which is causing the car to run hot.
You hp gains will not even be noticeable. Plus, to do any substantial work to the front of the motor, it would be wise to remove radiator prior to performing any work to avoid damaging rad.