You could get a Sound Blaster Omni or a Xonar U3.
I wouldn't get the E10 for gaming, as it has to be the first device in the chain (no line-in). I would rather spend that money on an amp with a line-in, in case you ever get an external surround sound device in the future. I haven't used Razer's surround (Razer Synapse is something else BTW), so I can't comment on it.
I guess I dont under stand the difference between a "gaming" external sound card and an DAC/AMP. I thought a the external sound card was a DAC/AMP and software for surround sound. I had looked into a Sound Blaster Omni before but was unsure of its quality to drive something like a AKG Q701. Also, for reviews that I have seen before, my Desktop motherboard had better sound than the Xonar U3, which is meant for notebooks.