You can fit other LUG mounted ones as well as RADIAL mounted with the correct brackets.
FRS/CUPRA R/PUG 406COUPE caliperswill fit with brackets and a LOT cheaper.
The AP's are wickedly good, but not that much better for the premium they command.
4wd brakes being single piston sliders are hopeless, even 2wd four pots would give a very marked improvement, went from 4wd cossie brakes to 2wd on my old sierra, MASSIVE difference.
If you get aftermarket calipers then getting a set of brackets made by brom or reyland will get them fitting/working well.
Don't forget to add decent fluid, braided lines, decent pads, people have thier favourite pads, some better than others for different uses.
Grooved and or drilled discs make a massive difference as they constantly deglaze the pads as well, I use drilled, and just change every couple of years as cheap, about £35 a pair.
I rate EBC REDSTUFF CERAMIC, and YELLOWSTUFF very highly and use them myself, despite being able to get any FERRODO FOC, but FERRODO have no feel, which I don't like.
As we are getting nicer weather(sometime soon!!) I will let you drive my car to see how the brakes are if you want.