Um... guys, there's more to it than Mic --> computer.
What soundcard to you have? How are you plugging an XLR mic into your computer, which, I'm guessing, doesn't have XLR input?
If your soundcard is just the basic motherboard integrated audio that most PCs ship with, that will impose a substantial and inescapable limit on sound quality. Remember, your recording quality can only be as good as the weakest link in your recording chain. The best mics and audio programs in the world won't help if your soundcard sucks.
Also, if you are plugging your mic directly into your soundcard, you have far less control over the input level than you would with a preamp or mixer (either one of which would be a very worthwhile investment if you plan to continue making live recording a big part of your mixing).