Antec NeoPower NeoHE 550 - Triple 12v rail system (18amps per) which is excellent. Is modular which is always nice. Seems to have compatibility issues with some ASUS mb's (A8N32-SLI Deluxe, A8N-SLI Premium, etc.)
OCZ ModStream 520 - mmm, only functions on a single rail, not too sure if I'd like that, even though the rail is rated at 26amps. Rail could be overwhelemed depending on what your system demands are.
RichPLS suggestion is a good one as the Antec TruePower 550watt does have a dual 12v rail system at 19amps per and doesn't seem to have any compatibility issues