Sounds like upgraded cams are already on the list. Fahr_side just mentioned the stockers have less lift than say the STI ones, impacting power at higher stage tunes, so your mods take care of that nicely.
I've not heard all good about barrels, some say they dont work so well, but have not read enough to make a decision on my own plans. I do like the barrels too for ease of positioning. PWR and Plazmaman are some I read a lot about as good stuff so far. Frozenboost also gets mentioned on the budget end of the scale.
Interesting layout you got planned, looks very doable and I've not seen one like that yet. Long thread on Nasioc and a recent one too on the 2.5 ej section there too to compare notes on.
i've got a 5EAT so no help on the manual trans parts but the other guys on here should have info for you.. Try the build threads up in the stickies too, some may be old but lots will still help for sure.