As mentioned on the PS tutorial page, I would HIGHLY recommend your PSU is a single 12V rail design. Many out there now show 4 12V rails, but they just aren't good enough for a high-end system, IMO.
I have a 550W single-rail Silverstone which is phenomenal. I don't think a 400W anything is going to be solid enough for the kind of system you're talking about here.
I would look for one with a 35A single rail. Also many of the cheaper PSUs get their 'max' power rating by beefing up the 3.3 and 5V rail amperage, which is something you won't likely see any real benefit from in real-world usage.
PC Power & Cooling, Silverstone, Etasis, Zippy and Delta are all great manufacturers.
OCZ Powerstreams are (or were) Topower-built units which have had their fair share of issues. I have seen a great number of serious strong PSUs for sale over on ocforums.com, but I think you've got to have 100 posts as a member to access the For Sale section.
I'd be happy to help you pick out a great, inexpensive PSU to run your new rig if you like. As for the great GPU debate going on, however, I haven't kept up with that the last year or more. MB and CPU are pretty easy to determine, as is RAM.