This problem is probably the mic or your mic technique. You say your vocals sound fuzzy, it's a good bet that you're overloading the mic when you record. If you're micing straight into your firebox you might want to consider getting a small mixer for your mic and run the mixer into the firebox and adjust your gain appropriately. Be sure to record about twelve or so inches away from the mic to keep from overloading it during the screaming vocals.
I use a cheap Harmony Audio firewire box for my audio and a old Behringer U802 mixer for mics and guitars, and both vocals and guitars sound great. The mixer gives you greater control of the sound input and will help you to prevent overloading the sound. If you're so inclined, you can even adjust EQ with the mixer and roll off some of the mic's bass, etc.
You also might consider getting a different mic. The Nady is a ribbon mic and they can be very sensitive to distortion. A good condenser or even a dynamic mic might suit you better.
You can pick up decent condensers for very little money these days. You might check into the Studio Projects line. Be be aware that condensers pick up A LOT of sound, so if your room is noisy, or for that matter, if your neighborhood is noisy, chances are pretty good the condenser will pick it up. Computer noise alone can kill a good vocal recording.
My solution to the problem is two-fold: 1) I use a dynamic mic. My mic is a Heil PR-30, which is a really terrific dynamic most often used in radio work. It does a great job of keeping unwanted noise out; 2) Once my vocals are recorded, I make sure to add a noise gate in logic, or sometimes even trim the vocal events to cut out unwanted noise. Thanks to the PR-30, however, there's usually very little of it.
Logic also has some GREAT vocal presets that you can add to the track. Honestly, the best vocals I've ever recorded were recorded in Logic. I've used just about every DAW you can name and Logic beats them all.
Hope this helps.