the audiophile 2496 and the revolution are both M-Audio products with the revo being newer and sporting somewhat better specifications, however the differences between the two are minimal in terms of sound quality from all reports (I've got the revo myself and have heard but not owned the Audiophile)
really you can't go wrong with the revo as it's drivers are optimised for home theatre and home audio use, the tech is newer and more advanced and there is a mod community swapping op amps, changing outputs and similar tweaks that you can draw information from. Probably the best place to find that kind of info is in the AVS forum for HTPC's...
I've used the revo with my modified ART DIO as a DAC and the SQ is very good indeed, now if only my PC was silent
