I have a similar setup with a Benchmark DAC and I'm running WinXP Pro. There is a huge difference with ASIO drivers. You may have to try some different software combinations. I've used Winamp and ASIO4All with the winamp ASIO plugin with some good success. Very crisp with ASIO, horrible without it. If you don't notice a huge improvement then somethings not right.
Also, you may want to try using a SPDIF connection to remove the ground connection between the computer and your DAC. I haven't experimented much with it since I don't believe I have a Coax out on my card...wouldn't use it either way for a computer setup... (cheap $24 chaintech Envy24 based card) but it sounds almost as good as my PS Audio Lambda II CD into the Benchmark, so it must be doing something right. Keep the connection as short as possible. I do want to try out some more expensive cards, but there's only so much you need to do when you put the signal into a good DAC as far as cleaning up the timing goes.
-Ryan
Also, you may want to try using a SPDIF connection to remove the ground connection between the computer and your DAC. I haven't experimented much with it since I don't believe I have a Coax out on my card...wouldn't use it either way for a computer setup... (cheap $24 chaintech Envy24 based card) but it sounds almost as good as my PS Audio Lambda II CD into the Benchmark, so it must be doing something right. Keep the connection as short as possible. I do want to try out some more expensive cards, but there's only so much you need to do when you put the signal into a good DAC as far as cleaning up the timing goes.
-Ryan