Seasonic has released their long awaited modular power supplies in 500, 600 and 700 increments, respectively. Those things are beasts. I’ve seen one review but it was taken down; however scouring many forums, I’ve seen nothing to indicate that these are less than stellar power supplies. These things are I believe direct replacements for the S12 line, the only difference mainly being efficiency as well as the cables being modular.
I hear if you have a local Frys in your town to check them out first as they have the 700W PSU for a little under $200. Newegg is selling the 700 version for $209.99 as of 10/3/06.
IIRC, the new Corsair power supplies which are modular are actually re-badge Seasonic PSUs. If I happen to come across a review or two I’ll definitely post it here.