These are the tried and tested from my mates who run MKIV platform track cars, not sure if all come in R32 size? We've researched this a lot on uk-mkvs.
In order of best first:
ATE Powerdiscs
Zimmerman
Nitrac 8 Grooves
Tarox although the G88s are unecessarily unfriendly to pads.
Pad wise: Performance friction, Pagid, Carbotech. I have Carbon Lorraine RC6s, I wouldn't put these on anything other than an Alcon disc though, as they'll chew through soft stuff. DS2500s are an excellent fast road pad, they're not good on heavy cars on track if you're really pushing on.
Now, the really interesting bit...
ATE also do a semi 2 piece disc like some Audis and the MKIV R32 had. The hub is aluminium too, so lighter. See
here N.B - yet to confirm if they do a 345mm disc.
Zimmerman likewise
here... or, even better,
here These are real!
If those come in MKV R32 size and I think the Zimms do, then along with ducting and your/Dave's calipers, I think you've found your holy grail.
Cheap floating 2 piece discs, Compbrake have some offerings off the shelf and Performance Friction have a massive list of rotors if you get some bells made up.