I went ECC a couple months ago and managed to find some parts that didn't break the bank, mostly because I held back and stayed a generation behind: GA-6UASL3, E3-1230V2. There are other sacrifices: the motherboard is rather no-frills, and the memory bandwidth isn't that great.

Besides price, another issue against server hardware is that it's generally designed for a server case and therefore doesn't play well with enthusiast cases. The board I got is a little odd in that it uses a layout more typical of consumer boards, though the socket placement is still not ideal.