I have an SB Audigy2, but I don't have 5.1 PC speakers (I use the digital out to my main system for DD/DTS pre-encoded content). Given that I don't feel like setting up goofy PC-only surround speakers, what's the recommendation on the best configuration for 3D sound w/ Doom 3? Will the Audigy do OK simulating 3D sound on a 2-speaker setup, or are there recommended headphones (or otherwise) for such a configuration?