well I think the 6600 gt takes 2 power connectors and basically requires a lot of power.
Oh and thanks for suggesting the Antec Sonata trotter, AFTER I ALREADY SUGGESTED IT.
Oh and you're getting that 6600 GT in the pci-e version right? Because I think your mogo is pci-e unless I'm mistaken.
You are going to want a good amount of power and while 380W MIGHT cut it I would recommend you got a little higher than that. I also think your mobo takes 24 pin but even if it doesn't you will want a 24 pin PSU anyway, with a shielded pci-e connector if it's a pci-e mobo.
I would spend the extra money and get this:
One of the best power supplies around, it's worth it to pay the extra. However if you want a cheaper power supply then this one is also nice.