I received mine today, and have found that my package is missing a power supply - so I am unable to give it a run :( Who is best to contact about this?
KyleLKyleL, I'm glad that AlexVallejo is giving you some good support here, but be aware that you don't strictly need the power supply to start using your new m9XX. You can use it without the power supply by connecting it to the USB on your computer.
Adding a power supply will increase how much power it puts out, but it is just a standard 2A USB power supply -- you might already have one laying around that would work. A USB battery pack would also work.
HappyMaxHappyMax is correct. Any 2A USB "charger" should work fine.
Regarding using computer power (stolen from myself off of head-fi.org):
Even if your headphones are driven to sufficient volume using the m9XX's lower power mode (using USB #1 for signal+power), I strongly recommend using both USB #1 (signal) and USB #2 (power) if it's convenient. For giggles, I unplugged the 2 amp power source from USB #2 and ran self-powered for a little while. The volume into my HD650s was fine, but I swore I heard a little bit of USB/digital noise being injected into the sound. After plugging back in USB #2 and the subsequent reboot, the silence was dead silent again.
My computer room is a mine field of spurious RF and noise and I'm connected via a powered USB hub via a USB docking station, so I may have the worst-case scenario, but for anything except mobile listening (plane, train, automobile), I'd use both USB ports to ensure maximum headroom and the cleanest power.