I wish my case have vents at the top for a fan too. Right now, everything's escaping to the back of the case and it is really warm, almost hot now. Especially being summer here in southern california, the room heats up fast and PC start heating up as well. My Athlon went up from 27 degrees C. to 45 degrees C at one time. Pretty big jump huh?
As for the power supply, I generally use a generic one from CompUSA. A 400-450 watt PSU would be nice to have. The specs for your new system looks awfully familiar and I swear someone in this forum has the exact same setup.
Get a case with one of those acrylic windows on the side (with a side fan of course). Then you can see inside and notice how pretty it is. As for the cables, get those rounded cables (for DVD burner and Floppy drive) to help with air circulation inside the case. For memory, good choice on using Corsair RAM. I guess you don't like the Corsair XMS suggestion. Anyways, do the 2x512MB or 2x1GB configuration in dual channel mode.
