Vette brakes would be the place to go if you want to keep your four-piston calipers. Quality rebuilds......
If you were to go with the single pistons, it would require a spindle change.
If you are looking for replacing the whole system, there are many companies as I am sure you are aware of. But if you are looking at keeping the remaining parts, rotors-lines etc, there isnt anything available caliper-wise to bolt on using your existing equipment.
The factory four-piston calipers used in the factory set-up, is an excellent even today if set-up correctly. If you want to keep them, check out Vette brakes. Other than that your choices are abundant in the brake kit world. You can put your own system together or purchase an all inclusive kit. I would really consider a kit from BAER Racing. It uses all the late model technology and the parts availibility for maintenence or replacement is second to none.
I guess it comes down to if you want to purchase a whole new kit or just re-build what you have.