Only onboard worth using is SPDIF out as it doesn't matter then. Probably my preference.
I had an M-audio great card for the price, have a Chaintech AV710 for cheap it is by far the best (sorry if they are hard to find now, I bought mine 3 years ago but bought one for Adrian on SSA 2 months ago for $12), and I have a E-Mu 0404. The 404 is the best out of the bunch sound wise, but isn't worth nearly 10x the price of the AV710. You only need two good ouput channels so it is a great solution.
I had a really old Turtle Beach, in the day they were the chit but have gone majorly downhill. The Audigy and other SB is gamer crap and useless for music in comparison with evertyhing else I have listed.
The best is probably the Digital Audio Labs card, but they don't come cheap. Used I have seen them for under $150, but pretty much painful for a used PC card. Unlike most though it is actually worth it. As far as I know from a testing perspective it is the only card on the market with phase matched stereo channels. The rest will have variance in phase and worse yet it won't be consistent with frequency
The DAL card is superb!!