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.
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. http://www.xoxide.com/coolmax-cr-450b.html
And it is pci-e. So like I said I would recommend you get the 6600 GT pci-e version as AGP will not work, and recommend you get a power supply with a 24 pin main connector and one shielded pci-e 6 pin connector like the ones I suggested. And since you are getting an SATA hard drive you are probably going to want an SATA power connector as well. The ones I suggested come with those also.
I would really recommend you spend the extra dough and get the OCZ. It's a really nice power supply.
After a little searching this is about the best I could find: http://www.newegg.com/app/viewProductDesc.asp?description=17-153-022&depa=0
It's a little pricey but it's well worth the price.
It is 460W so it will provide you with plenty of power. Also it has a 24 pin main connector, a 6 pin pci-express video card connector, 2 5 pin SATA hard drive connectors, and all the wires are nicely sleeved. Also it has a large fan so it will be very quiet.
Also I checked out the specs on it and it is standard ATX size, so it will fit in that maxtop case.
It also has a blue LED if you are into that stuff.