Recording Guitar... Questions About Preamps Etc... Options

[Righteous Bullet]

ok i know its a good idea to use a preamp for recording direct with guitar. this is a dumb question but im wondering if you should use it with a mic too. The reason i ask is because i am (for the time being) micing my amp sending that into my mixer and then mixer hooks to the pc, and im using free software just so i can record a little and get my ideas down since i dont have a good setup yet. Anyway when i record my amp with my guitar distorted it can often sound pretty crappy and im not sure why, and i think there are preamps in my mixer anyway... is this something i should fix with the sofware? like use a compressor or something? or what?