from personal experience: pde up and downpipes are good pieces. although now looking back i think i should have gotten something with a divorced wastegate section (seperate pipe for the wastegate, rejoining the exhaust about a foot and a half down the downpipe to minimize turbulence)
bov's... hks is a fine piece. it is designed in such a way that it is nearly impossible to make leak unless the seal on it is compromised. very nice unit, IMO.
the forge bov is also nice, but i have leaking problems now and then with it when i'm running a slight vacuum (around 2psi or so vacuum) it seems almost unrelated to the spring (which is odd..) but it's not a big enough deal to worry about. very slight sneezy pfff sound is excellent when you are going into cities with lots of cops, and when your girlfriend hates the hks's sound
for the uppipe.. it's really a personal preference. i'd say get whatever you can get for around 200 or less. as long as it isn't junk quality or a bad name maker, you should be fine.