Medium boost..? As in you could run 30psi on your block, but run 15psi? Anyway, the gt28r will only support up to 350hp (not taking any bearing swaps into account) while the gt30r will handle up to 500hp.
Take a look at the Evasive Illusions Myspace page
www.myspace.com/evasive_illusions There is a video on there (unless it was recently changed) that shows a yellow civy hatch running a boosted itr on a gt35r. it's a youtube video and the same guy/car ran a gt30r prior to that putting down good numbers. I'm doing the 550hp itr build so our builds will be "somewhat" similar. I don't know what kind of money you're looking to spend all together, but the better built your block/head the better off you'll be. I fully agree with the dude about your tranny selection, especially if you're not looking to have internal gearing done. Pick up an LS tranny and LSD it. One of my guys did it on his EK/LS and had no problems.
pistons/rods - crower, eagle, etc.. nice and strong
tb - skunk2 or edelbrock 68mm ftw
a mani that will retain a/c.. good luck, not even on my radar
downpipe - 3" no one specific, ebay, megan racing.., local shop..
ecu - hondata s200/s300 depending on what you want, just tune it
valves - titanium valves and retainers, haven't heard anything good about skunk2, suggest crower
cams - AEM
radiator - mishimoto, although there's plenty of cheaper suitable sups
Hasport CV's level 2.9.. they're cheaper than DSS and support in excess of your goals