I heard that it's possible to find re-purposed Brembos for non-Brembo 11-14 GTs but I can't find any links on information for them. If anyone has a link that can be passed along that would be great.
See "So you want Brembo brakes" thread in this section.
Be aware that the the calipers offered at Autozone/Advance/Etc and now Chinese reproductions and not authentic Brembos that have been rebuilt. Personally I would search for someone selling a used Brembo take-off kit.
Be aware though that the packing from the ford performance one is absolutely terrible and I ended up returning it twice because the calipers were scratched.
The vorshlag kit has some nice upgrades too so I would recommend going that route if you have the cash.