If you are speaking only of headphone amplification, there aren't many in the pro arena that JUST make a great amp, (they are normally coupled with other things).
If I were to just name great headphone amps in pro audio that approach (but don't meet) Geshelli - 1) Rupert Neve Designs RNHP 1-channel Precision Headphone Amplifier (a more warm sound...sounds like a smooth, but accurate sounding tube. Good for MIXING); 2) Little Labs Monotor 2-channel Headphone Amplifier (closest to Geshelli's vibe, but still not quite as good. Great for MIXING, okay for MASTERING). All of the solid-state THX hi-fi stuff is mostly better for pro audio listening than either. But the ERISH BALANCED...nothing.
If I were to list great headphone amps built into other pro audio equipment, I have to split them into the MIXING and MASTERING categories:
MIXING: Burl Audio, RME, Universal Audio (prefer these modded), Antelope Audio, API, Coleman Audio, Grace Design, Dangerous Music, Solid State Logic, Heritage Audio, Neve, and MOTU (certain higher-end ones).
MASTERING:
Lynx, SPL (higher-end stuff), Shadow Hills Industries, Crane Song, Dangerous Music (high end stuff), Burl Audio (high end stuff), Bricasti, Benchmark, Chandler Audio, Sontec, Lavry, Mytek, Tegeler Audio.
If you are speaking in general terms of quality companies in pro audio (mixing and mastering), there are certainly more to name. Let me know if you want them, (specific uses, whatever). I have used or have owned something from just about everyone that has made equipment since 1988.