the guiy to go to is DaveB1970, he's the resident brake expert
he sells a kit on here with Cayman 2.7 4-pot calipers that actually use the standard GTI/Ed30 312mm discs. braking power is plenty for the track and for some who have 300bhp+, but is at the same time light with cheap consumables. if you speak to TFSI_Mike, he's run both. i think he said the braking power is equivalent, but the lightness means they are better. plus you can always put track-spec pads in them
it may be possible that the Cayman 3.4 4-pots may be suitable with this set up if you're keen on bigger discs, but you'd have to consult DaveB about this - i think the disc is too wide or something.
good luck!