thYou need to get carriers which are custom made for 5 x100 pcd golfs there about 98 quid delivered of ebay but i know the guy an dhe can do them slightly less... the boxster s rear calipers are same as 996 rears you can use them with standard 312mm discs or you can use upto 325 ..
you can get shins and pics and what not but if you get the complete caliper then the whole thing comes complete liek the ones i got ... the calipers go for around 200 -300 depending on condition...
theres a guy called daveb on uk mkivs hes good with brakes andhe guided me as to what to get... the braklines from him are £45.00 free delivery there the braided ones....
you can basically get any caliper to fit depends how much you want to spend but am a tight paki bastard so i wanna save money and just use what i got (i.e my existing 312mm ) later i may upgrade them to 325mm if i can be arsed but ad rather get better pads, coz all discs are more or less the same its the pads that make the differece.
am gonna chop my existing pad loom and fix it on to the porsche pads so that the wear indicator is still active ave also ordered the proper hose brackety sh!t from vw for 15 quid ...am just waitign for carriers and brakelines to arrive and then am gonna fit them on