I've a sparingly used headphone amp - Matrix M-Stage with the optional Burr Brown OPA627AP upgrade. I bought this July of last year, and has probably seen 5-6 hours of use. I just am not a headphone guy

I sold the sennheiser HD650 that i had last year, and since then it hasn't seen any use.
It has two inputs, and you can use it as a simple preamp as well. I found this feature to be extremely useful. It sounded great when i connected it directly to my amps ... though i didn't use it as a preamp for long as it lacks a remote, and i like to fiddle with the volume from where i sit. It paired very well with my sennheiser HD650 but mentioned earlier, i'm not much of a headphone guy. Just that the headphone around my ears makes me a little uncomfortable. I prefer to listen to music while i'm working or doing something else. Of course, none of this is reflects on the amp's performance. It is a very nice unit, and bears a not-so-subtle resemblance to much more expensive lehmann black cube linear headphone amp that costs in excess of $1k.
I paid $300, and am asking $225 shipped from 75025 to anywhere within continental US.