So I guess it would be between Corsair HX-650 ATX Power Supply Unit or Antec EarthWatts EA-650Watt. PSU or Antec TruePower TP-650Watt. PSU or Antec HCG-620 High Current Gamer Gaming PSU.
But currently the Corsair is sold out, so I would have to wait.
Which cards are you considering for a Crossfire setup.? Obviously you know that Nvidia cards (like your 9800GT) cannot be used in two's (SLI) on your board.. As for staying in the 650 domain, also check out the XFX XXX 650W and the Seasonic S12II 620..