[Moppie]

I have no idea about the GTs, but I know the JDM WRX if driven correctly is a little faster than the New Zealand Intgra Type-R (RSX), but were talking 100ths of a second, important at the drag strip, but meaningless on the road.
Out of those two simple chosse the car you like the most for your own reasons.
However the USDM WRX has less hp than the JDM version, while the RSX has as much hp as the New Zealand Integra Type-R (200hp) and uses the same suspension and brake set up.
I think you will find that in stock form it will be faster.
But of course the WRX has something the RSX dosnt, a Turbo, and winding up the boost on a WRX, and replacing the stock exhaust will lead to some very easy and noticable power gains.

But then you might enjoy driving the RSX more, and not be bothered by it being a little slower in a straight line, becasue if driven correctly its easily a match for the WRX in the corners.

(if by GTs you mean the Celica? then its deffintly an also ran to the RSX and WRX, unless of course you happen to enjoy driving it over the other two, then its becomes the better car.)