I agree. You should always invest in a good set of speakers and/or headphone BEFORE considering the purchase of a better sound card. Cause with better speekers, you KNOW you will get a BETTER audio experience. As opposed to maybe (if the speekers are not good enough) getting a better sound experience with a sound card upgrade.
What would be nice is a sound card/PhysiX engine on one card! Using PCI-e, I think it would be achievable.