OK, ended up going with the Athlon II X3 Rana, and after reading more about the motherboard, switched to this one by ECS because apparently some people were having issues with the Gigabyte board with triple- and quad-cores.http://www.newegg.com/Product/Product.aspx?Item=N82E16813135233
So, total cost ended up being $264, with $28 in rebates.
Went to the local Fry's to see about cases, since that's one thing that's almost always $15+ in shipping if ordered online. Turned out they had an Antec 300 for $39.99. Recycling the optical drive from the dead machine rounds things out nicely.
So, looks like total finished cost for this build is going to be $276. Helps that I already have a copy of Windows, and that no video card is needed for the time being.