I would not discount
all Whiteline products. I was one who ordered the Whiteline UCA during the time it was failing. I never installed it and was able to return it. I also have ordered and installed Whiteline's adjustable
Panhard and brace and they are a very high quality product with no issues. Just to add, you are going to want to beef up at least the rear
suspension to handle the power and to get it to the ground. I, myself, have not desire to bump the power beyond a good tune and am more interested in handling characteristics so, I've been going down that road with mine.
As far as brakes, My '11 GT I had previously had
brembo's and I thought they were great so, I'm looking at getting the new kit that has a complete replacement of calipers and rotors that include 15 inch rotors in the front. That 's just me though and may be a little more extreme than you may desire. The suggestion of stainless steel brake lines is a good one as it can improve the soft feel of the brake pedal. A good set of brake pads will also improve your brakes over stock as well and may well be the route I go to first before going 'extreme'.
I, too, also like the GT/CS wheels and if I could get a pair with a 10 inch width, I'd buy 'em. But, they don't seem to make them wider than 8 inches so mounting wider tires from stock is, at best, limited. I want to go with 245's front a and 275's rear.