What you probably read is that the best way is to use a mic preamp, which are often found in mixers. Reason being that your soundcard's little mic preamp isn't exactly optimal and may not even work. Thus, you use an external preamp (either standalone or in a mixer) and run it to the line input on your soundcard.
If your mixer has mic inputs (mic preamps) and a line out, then yes, you can certainly try to use it. How good it sounds, well, you'll have to see!
Slackmaster 2000