Request help purchasing lighting components

Hi guys and gals,

I'm considering the option of buying the parts to build a 250w or (preferrably, if within price range) 400w HID setup. Is there anything I should know about those ballast "kits" being sold on ebay for dirt cheap? Anything in particular I should avoid?

Here's what I know I need so far:

-Remote Ballast OR ballast kit + ballast enclosure.

-Reflector (I like the bat wing shaped ones but if others are recommended I'm not stubborn)

-Mogul bulb socket

I have absolutely no interest in the all-in-one kits where the ballast is attached to the reflector and that heavy crap hangs ominously over my friends (not to mention turning the grow area into an oven)!

How hard is it to throw one of these things together? I have basically good electrical skills.

-N2P2K

[edit:] Oh yeah, HPS, not metal halide (unless for some unknown reason I can acquire an MH setup cheaper and use conversion bulbs during flowering, but to my knowledge HPS is cheaper per watt)