380w is enough, despite what everyone else claims to say. A beefier PSU definitely WILL give you more headroom, but unless you plan on using dual video cards, I don't see it being very needed. My current rig is run off a 380w PSU (funny, according to the eVGA box, my PC shouldn't be able to run the 8800GT at stock settings, nevermind overclocked.)
I also have 5 hard drives and an optical drive, so I do have quite a few extras putting pressure on the PSU, but I'm idling at 120w drawn from the WALL and loading when playing games at just around 200w.
Get whatever is cheapest really, but efficiency is key.
Edit: Typos. I really need to start proofreading my posts earlier...