If you don't want to spend the money you would on a Ludespeed kit, then assemble a Legacy Kit, which is basically the turbo parts off of a 91-94 Legacy turbo. This is my setup:
Legacy Uppipe w/20mm spacer to clear heads
WRX OEM Downpipe
Legacy IHI RHB5 turbo @ 5psi
Vortech FMU w/6:1 plate
WRX OEM exhaust
Rallispec TMIC
GReddy BOV
ACT Clutch
None of this is on the car yet, and this only about half the stuff, but it will have end up costing me about $3200 in the end.
Graham