The Intel Avoton platforms are spendy but attractive: ECC support, low power, AES-NI support (a huge boon for encrypted pools). On the desktop side of things, there are Core i3 platforms with ECC support, and of course there are many options in the server arena. The single socket E3 Xeons are popular in the community, and of course for higher end systems, the dual package Xeon platforms are well supported.