Hi, I use the line in on my pc, but I just bought an iMic, which uses a usb interface, they claim it sounds better since its not a sound card or something. I used it to record my school play onto my laptop since it doenst have a mic in. Its about 35 dollars, and I think it works pretty well. I haven't actually tried acid pro before, but I've heard it's a good program. I use Audacity, I think it works pretty well, its what I used on the songs I recorded. Its got a bunch of good features, I think. But it's real easy to use, and best of all free. Hope this helped. Peace.
BConner