I believe the USB device takes a surround signal (5.1/7.1) then virtualizes it for stereo headphones which are connected directly to the USB device via a 3.5mm jack.
*You can NOT get a proper surround signal from a 3.5mm jack as that only contains stereo data.
So, provided the USB device does what I think, then any set of stereo headphones could be plugged in to it and have virtual surround sound.
ASUS has a new Z97 motherboard (hero VIII?) that has an onboard audio feature that can do real-time virtualization that is output to the Front Panel of the case and works with STEREO headphones.
1) 5.1/7.1 signal ->
2) Signal virtualized by USB device then converted to analog ->
3) 3.5mm stereo headphones experience Surround Sound