Your Muisc Streamer has a headphone jack?
I dont think one needs to spend so much on an amp for such headphones. Rather one should get a nice DAC which can also doubles up as an amp. I tried my friends Denon D5000 directly from my Music Streamer II and I preferred that sound to the sound from my MS II -> Audio GD Compass amp.
The Music Streamer II IMO is a very good DAC and its very cheap to boot. IMO it can drive cans like the HD650 pretty good.