For those on the budget you can still find used Emotiva BasX A-100So that's 2.6W at 150ohms. Definitely not a lot of amps that can do that, very few under $1000. Flux FA-10 which has been recommended seems like it can probably do that much, not sure if there's anything else..
Power Output (headphone output; direct drive mode)
(requires internal jumper; USE WITH CAUTION):
8 Ohms: 50 watts / channel
33 Ohms: 12 watts / channel
47 Ohms: 8.5 watts / channel
150 Ohms:2.6watts/ channel
300 Ohms1.3 watts / channel
600 Ohms:0.6watts / channel