I read the thread, they were talking about the 2 pot version (Porsche released a new 4 pot rear caliper on later models )
I'm afraid that's incorrect matey. The calipers discussed in the other thread were 996 rears, which are also 4 pot.
In buying these calipers. you could have let yourself in for some bad luck. none of the porsche rear calipers have large enough pistons to work properly on the front of an S3.
As said above, when comparing single pot calipers to 4 pot calipers, you only take one side of the 4 pot into the equation. as in a single pot caliper with a fixed opposing pad, the opposite pad applies an equal and opposite force.
So, your 964 rears have roughly HALF the hydraulic stopping power of your standard 312's.
The reason your ducatti brakes are so good, is that the pistons are matched to the master cylinder.
The reason rear calipers cannot be used on the S3, is that the master cylinder remains unchanged, so you need to match or better the piston area to retain good braking.
In theory, the rear calipers could be made to work well using a TINY master cylinder, but that would require a redesign of the rear calipers we well.
If something looks too good to be true, it usually is.
I contacted this same guy about a set of these recently too, and he was unable to tell me what the calipers came from. SO they were instantly dismissed.