NeRP is right. I get amazed at how many people buy a sound card without knowing that. You'd much better get a faster processor that can handle realtime MP3 decoding, cause then you'd get both speed and the sound you want.
You have to use calibrated, it makes a big difference on some systems. The procedure is a bit tedious to learn on the docs and all that, and sometimes you won't get it right at first, but you won't regret it.
You'll be amazed at what Paula can do.
Paula rocks!
