Uh well for generic 2.1 audio and if you're not an audiophile, motherboard "HD" audio will suit you fine. Otherwise, well, really depends on your budget. Sub $100 something like Xonar DX (the slim one) or Creative XFi Titanium would be ok (or the HT Striker Omega I hear is good). If you want a big step up for only a little more cash, AuzenTech Bravura or Forte are great. If you want more, Xonar D2X or AuzenTech HD HomeTheater are rather good.