Want to chime in here.
I didn't "upgrade" exactly, but I did a full install of Wagner Thermoquiets with Wagner rotors on my 2006 GTP and I am quite pleased with their performance. Pedal travel is a lot more than I'm used to with other cars, however, when I need to get on it the brakes will stop me perfectly.
Price for front and rear pads and rotors and four cans of brake parts cleaner (only used a can and a half on the car but also use the stuff to clean my guns) was $359.81 from O'Reilly.
Tools needed; Jack, jackstand, tire chocks, 6 inch C-Clamp, 6 inch pry-bar, mm socket set (especially 10mm, 13mm, 14mm) and mm wrench set (a breaker bar or long 3/8" drive ratchet will help also) and rent a set of caliper tools to compress the rear calipers...or use a pair of needlenose pliers and get ready to cuss a lot.
In case this is the first time brakes have been replaced on your car, your rotors will have Dammit washers on the studs; Two per wheel. I named them dammit washers because you have to basically destroy them to remove them and will yell "DAMMIT" or worse while getting them off. They basically hold the rotors on at the factory on the assembly line until the car reaches the tech. who installs the tires and lug nuts. I'd recommend channel locks, a flat blade screwdriver...maybe even a pair of diagonal cutters (*****, wire-cutters, etc.) to get them off.
Tip: When compressing the calipers, put tension on the ram of the caliper with the clamp or caliper tool, then crack open the bleeder valve (have a drain pan ready and GO SLOW because fluid will squirt out when compressing the calipers) and compress the calipers the rest of the way. This will prevent the crap that has built up in your calipers and lower lines from being blasted back up through your brake system. If you go this route, have a can of DOT3 or DOT4 (NOT DOT5) ready to top off the reservoir after each wheel.