howdy mate! id say sort the handling first, anti roll bars and drop links, set of eibach or whiteline springs or bc coilovers and then proper geometry setup will make a massive difference
i had mintex 1144's on my car and far prefer them to the ds2500's i have now, braided lines and 5.1 fluid are well worth it though and id stick with standard discs unless you shell out big time for performance friction or similar
powerwise id also check out trackhound tuning for mapping, got some very happy customers and cheaper than Andy F - coupled with a decat, panel filter and upgraded plugs i got 350hp on my sti. if youve PPP you should already have a 255 fuel pump
good luck with burning out your flexible friend