Having heard a few of the popular high-end favorites on head-fi, I don't feel bad at all about the not-quite-as-revered amps I have.
But in terms of non-portable gear, about the only dedicated headphone amp I still find a use for is the Violectric HPA-100, for driving IEMs when I'm at home. Sometimes I'll use it for full-sized cans but on the whole I prefer my receivers.
If the HK 670 had a -20 dB switch like some of the Pioneers and Sansui have, I'd probably not need the Violectric either, or else I'd consign it to my other office.
(Although, frankly, I'm mostly interested in using a 100 WPC amp to drive 108 dB efficient IEMs because the disproportionate scale really amuses me. As if it were possible to fit a Jaguar E Type engine into an MG Midget.)