You could always opt for an even older, yet very interesting setup. For example a Core 2 Duo E8600 + Asus Rampage Extreme ( X48 ).
8600s should go for as low as $15 on ebay nowadays.
Don't know how easy it will be however to locate and grab a good mobo for it for LN2.
In order of preference you should go to:
Asus Rampage Extreme > Asus P5E64 WS Evolution > Gigabyte GA-EX48DQ6T = Asus P5K3 Deluxe
Very fun setup!
If you'll go VGA LN2 as well, dig a GeForce GTX 280