I'd say you pretty much got the mods sorted out
1. Up pipe - I'd definitely change this as it has a pre cat in it and I've heard that these can break up and if it does it's bye bye turbo
2. I'd go for OE ported headers, i had mine done by Harvey Smith harveysmith1@btopenworld.com but i believe API engines http://www.apiengines.com/index3.php do them as well but they are not on the website, they will improve the spool up of the turbo which basically means the turbo will start to boost earlier
3. Samco hoses, not really necessary apart from the turbo to intercooler pipe because the standard one will probably split when the boost is increased when remapped
4. TMIC, advisable to change it but don't go for one of the cheap ebays jobs, try and find a STi intercooler and as long as you get the pipework with it it's a straight swap
5. K & N panel filter, or green panel filter, don't really think there much difference in them but the green filter seems more popular
6. Uprated fuel pump, not 100% necessary but it's worth changing it anyway
7. Remap, there are many (Andy F - Zen Performance to name just 2) but i personally use Bob Rawle (if hes good enough for Roger Clark motorsport then hes good enough for me) but you could also try Jolly Green Monster who has remapped Dunks, Deani_age & Daniels cars, as to cost it can be anywhere from £400 to £600 depending on whether they use the EcuTek software or something similar but it's well worth the money
Clutches & Gearbox's, I'm currently running 333bhp & 325ft lbs torque with the standard clutch & gearbox, the clutch is fine as long as i don't launch and even then it doesn't slip but it does smell a bit but i think i will be changing it soon just to be on the safe side, they say the gearbox is good for around 300bhp & torque so really mine should be playing up but as yet I've had no problems with it (that will be the kiss of death for it now)
If you need anymore info please don't hesitate to ask [Y]
Ian