all i can say is the wrx pretty similar in weight i think to the mspeed 3. and 3 30 min session of hard hard braking pads were gone. my friend tried the same thing on his sti. etc.. same result.
but if you drive carefully and slow then hp plus would work but then its not as fun. Its safer to spend the extra money on good track pads, street pads will not be safe enough for me at least.
Porterfield were very very helpful. just give them a call. According to them they can take any material they carrry which is a lot and put them on any pad you want! and the price was reasonable. i used raybestos st41 i think it was because thats all they had at the time and i needed the pads in 3 days.
raybestos was a little more expensive than some other comparable stuff.
also ive ordered from cobalt friction race pads for my integra and it worked out well, i had good results from both places, porterfield is in socal so it was local for me
but def upgrade pads for HPDE events and upgrade fluid to ate blue or something like that