7kg per wheel in unsprung weight is quite alot is it not
312 kit=13.5KG 345 kit=20.5kg per corner
And the 350x34mm kit complete with 6 pot front calipers from a GT3 RS Porsche is probably nearer 21kg per corner, you need mass to deal with the heat. Anybody gone tracking with 25mm wide discs knows that.
Obviously if you have £1700-£2000 quid to spend on brakes then we can get lots of boxes ticked but if you are planning on putting £400 into a set of discs and still using iron calipers then its the wrong way to go in my opinion. Better to deploy that money into something liek some Porcshe calipers and having probably 30 different pad compounds to choose from as opposed to the 2 or 3 you can get for a S3/R32 setup.
I'm not having a go at the R32 setup at all, its a great £3-400 upgrade whereby you get £3-400 quids worth of improvement over the stock 312's so by definition good value. As long as you are aware of its limitations, operate within them which means the odd "non hardcore" track day and they'll be great. It may be able to do "Harder" core trackdays with some cooling ducting and some custom made pads
As in most forms of motorsport you can quickly get into the realms of diminishing returns for the more money that you spend, spending greater amounts for smaller improvements. I would suggest that you spend the money wisely and get as much power/stopping for your money as you can.
Edition 30 owners with Pescaras will ultimately need to realise that they are hog-tied by those wheels with very limited room for any upgrades at all. It would either be the B5 RS4 setup (Good pad availability) the Mk5 R32 /S3 setup (Crap pad availability) or the aforementioned custom £2000 setups probably based on a 28mm wide disc as there isn't much room for anything much thicker.