Specs: Best headphone amp: max 43cm wide X max 7cm tall, in silver color, money no object
Will drive: Beyer T1; Grado RS1; Ultrasone Ed. 8
something like this?
Buying a headamp based on size and colar is quite strange but very well... here you go.
This one is good, if a bit expensive maybe. But you did say money no object.
If you're willing to consider other sizes/colors there is also the new Bryston BHA-1 which should be quite good and versatile. Or maybe a burson HA-160 or soloist. Or a Violectic V200. They're all good - different in some respects but all good.