Only temporarily, I am amping them with a FiiO E17. However, at the same time I ordered the HD 650s, I also ordered a FiiO E09K to supplement my existing FiiO E17. The HD 650s arrived first, but the FiiO E09K is "in the mail" and should arrive any day. The HD 650s are sounding great with the E17, but I ordered the FiiO E09K in order to have an appropriate upgrade in the amp department (within my budget) at the same time.
I got the HD 650s from American Musical Supply, which is an authorized dealer. I'm also claiming the $50 rebate that Sennheiser has on the HD 650s through the end of April if they are purchased new from an authorized dealer. I ordered the FiiO E09K from the Micca Store, which is an authorized FiiO dealer.