I would look at the Asus A8N-E, which is a very good PCI-E board. The user manual has a list of tested memory, but obviously other memory would also work. I used Corsair TWINX1024-3200C2PT (2 x 512) which is very stable. It will work in DIMM slots 2 & 4 (or obviously 1 & 3) to run a bit cooler away from the CPU. You will want to replace the MB chipset HSF with a Zalman passive chipset cooler for $10.
If a moderate PCI-E video card is desired, then the ASUS Radeon X300SE Video Card is a possibility. If you want a 9600 or similar, you will have to go with a AGP motherboard.
Given your fairly modest video card, the Seasonic S12-380 would work fine. I am using that PSU with a 3500+ and 6600GT and 2 hard drives.
The Antec SLK3700-BQE or SLK3000B would work as a case (the SLK3000B has side CPU vent hole, but I don't think you need that, and would increase noise a bit. But the 3000B comes without a PSU, and you would have to sell the PSU included with the 3700-BQE (You can easily get $25-$30 on eBay for the PSU).
If you get the 3700-BQE, this drive mounting system will make the hard drive inaudible:
http://forums.silentpcreview.com/viewtopic.php?t=10450