I have an old BH5 Legacy that I use for towing the rally car and once I used it as the zero car on Targa for a day. I have 4 pots with EBC Blue pads (which are nothing like yellows), and on good tyres it was quite good to use on Targa. Bearing in mind as the safety car and with no notes I couldn't go as quickly as the competitors, but we also have to stay in front of them, so plenty of hitting speed limiter and carrying as much corner speed as a 20 year old car with stock suspension will let you. Even found a pic of it:
http://www.proshotz.com/p170609214/e235944cb
Anyway, I found 4 pots with good pads sufficient. Track maybe a little different depending on how tight it is for getting sufficient cooling on the straights, but brake ducting makes a massive difference with that and is cheaper to do than upgrading pads.
Only thing I found is the race pads aren't much use on public roads, noisy and dirty and a bit lazy on the first couple of applications. So best to only use them when racing.
SP500 pads I have only used once, years ago in a friends STI at Manfield and they were fine on road tyres. I think you would cook them if you push them on semis.