STi TMIC... is beneficial enough. JDM STi TMIC is best IMO. NO FMIC as if it may/will reduce inlet temps it will lag the hell out of your turbo. Even so, GT35R WRX's also run TMIC's... typically going larger XS units. If you're worried greatly of heat then buy an IC cooling spray unit similar of OEM STi setups.

Rotors... slotted if you must other than OEM, but pads, fluid, SS lines, and Cusco BMC brace will do wonders!!!

Exhaust... buy something other than OBX, please. Don't cheap out as welds will break over prolong abuse, or muffler insides will fall apart, maybe both. DON'T say you won't beat on this car.

Intake... 2nd gen Perrin inlet w/HKS panel drop in.

Sways... Cobb or Whiteline, and DO pick up endlinks like everyone is suggesting.

EM... Get it ASAP before power adders. It's cheaper than half the stuff you've bought/will buy, so there's no excuse not to. Between Cobb AP & UTEC, I'd suggest buying whichever one a tuner nearby is consistent with tuning on a regular basis. IIRC, Kienan does UTEC.