After a lot of thought, I went a completely different route. I ended up buying a Topping TP30. It's a small, but high quality t-class amplifier with a built-in USB sound card. I'm running this into a small pair of bookshelf speakers, though it does also have a headphone jack on the front.
The pros of a setup like this is that you avoid pretty much any interference due to the sound card being in the amp, and not the PC. You also get something that can actually drive speakers, unlike most PC sound cards.
The cons are that there is probably a bit more lag, being a USB sound device. It's a purely stereo setup, so no fancy dsp or surround features. There is also no mic input. I have a seperate pair of USB surround headphones that I use for games, and my webcam also has a mic on it, so this wasn't an issue for me.
Just something to think about.