Why no love for the Headroom Blockhead?
I've owned mine for 5 years, just got the most recent modules from Tyll a few months ago, and love it. I've not owned any other high-end headphone amps, but the Blockhead is good enough that I don't miss my speaker-based set up (Quad 988, McIntosh MC275).
The Blockhead has a lot to recommend it: reliable, from a mfr that's been in business some time now, and is likely to stay that way. And probably a relative bargain in the used market, if you can find one. Otherwise, there's the new Balanced Max, which I've not heard, but uses the same modules that are now in my Blockhead.