pretty much as above - the exhaust system is pretty darn good all the way to 200hp so i wouldnt bother with that
(bare in mind varex systems are now illegal ggrr)

Intake the choices would come down to Fujita CAI (top end) or Comptech Icebox (tonnes of torque)
the next point to address is the headers ... WeaponR, Toda, Comptech, etc
then you would look at either underdrive or lightened pulleys ... Unorthodox Racing or Ralco RZ
next up would be clutch and lightened flywheel and a good set of tires

from here things get a bit more expensive - the next move to make is getting an ECU
the best value for money unit available at the moment is getting the TSX ECU with Hondata Flashpro
it will allow you to lower vtec slightly and tune in your existing mods
once you have the ECU it opens up the ability to fettle a few hidden secrets of the ole euro
the first one being the intake cam - the american TSX intake cam was a LOT better than ours
making it a fairly cheap bolt out mod - but you do need ECU to tune it in
the next hidden gem is the VTC - the K24 can handle a VTC range of up to around 40deg
standard it is set at 25deg - so either you get a replacement thats set to 40...
or you buy an RSX/Dc5 50deg VTC then install pins to limit it to 35/40

at this point any additional power would have to come from turbo or supercharger

i would highly recommend getting a good rear swaybar as well - dramatically improves handling

good luck and have fun =)