While this mainly the purview of Tyll Hertsens over at InnerFidelity
(make sure to check out his show coverage for all things personal listening), the drop dead classic looking (its the meters) McIntosh
MHA100 Headphone Amplifier ($5,000) also includes a pair of speaker binding posts strapped to a 50W amp so you can "...enjoy your desktop speakers instead of your headphones" according to the MaIntosh marketing literature. You'd have to have one big desk. Also from McIntosh, "Employs new adaptation of McIntosh Autoformer technology to produce three headphone impedance ranges of 8-40, 40-150 and 150-600 ohms so every headphone will receive the optimal McIntosh sound." Inputs include Coax S/PDIF, Toslink, AES/EBU, asynchronous USB, as well as 2 analog inputs (XLR and RCA). Outputs include a 1/4" headphone jack, the aforementioned speaker binding posts, and a pre-out for connecting a subwoofer. The MHA100 can handle files with resolutions up to 24/192.