Well I seem to have made a blunder. I've apparently been using my motherboard's onboard sound the entire time, which doesn't have an option for Dolby Headphone but rather 'DTS Surround Sensation UltraPC', which gives a very crude effect compared to the Dolby Headphone plugin I occasionally use in foobar. While I do not like Dolby Headphone for music, I cannot comment regarding its use for PC gaming. I feel very silly now. My Xonar DX is currently unusable due to terrible C-Media drivers being terrible.
Heh... glad you figured out what was happening :)