I do have one but I haven't tested the surround sound. I think the software is only needed for the software-based Xfi stuff; the X3 has an optical input as well as discrete surround speaker outputs so I would think it would work.Do you have the X3? From what I've read online, you do need the Creative drivers if you want surround sound. Else, Windows stock driver limits it to stereo only.
To the OP/TS,
You don't want intermediary device but want something that can drive 5.1 speakers. Well, the closest thing you can get is an AVR because of the amps. But that can't drive a subwoofer. AVR via HDMI is a pain because it's treated by your PC as a monitor. SPDIF optical isn't ideal because you need the PC to encode it to AC3 first, which adds lag. For the headphone support, it will not meet your needs. Alternative is a Creative solution but I'm sure you are already well experienced with that (AE-5).
I understand your pain looking for such device. I'm feeling the same too. I love surround sound on PC. I have 5 units of JBL104 for this, all connected to my motherboard onboard Realtek audio. I can't find any good setup at the right price. Majority of good multichannel USB DAC are those meant for professional audio and cost a bomb. I'm not getting a Creative because I've heard too many bad news about them.