No issue with running 300mm rotors with the HP's, as the spacer kit you get with them will be made for the 300mm rotors which are stock.
I run braketech wave rotors and no complaints thats for sure, running Brembo HP's, 19x18 brembo master, SBS sintered race (not recommended, very hard on rotors) & goodridge SBK lines..
I would say if you want to waste the money get brembo 310mm rotors...the 320's might give you some way tighter cleanace when putting the calipers on/off.
also they will be a bit heavier but more initial bite when braking.
If/when i mod the brakes again i will try the Braketech 310mm CMC rotors as lighter and will help the handling and work as well as anything else made period.