Well, you sure do have a lot of options at this point. I would first improve your sound quality with what you have first b/c you need to know where the problem is so that you don't repeat the same quality issues by replacing something that may not be the point in the sound chain that's at fault.
If your sound quality issues are at the mic, cable, pre-amp, connectors, eq, other outboard processors or effects, mixers, levels at each, mic placement, room, sound source - instruments vocals amps levels of them, then if you record the problem by capturing it better, it may even sound worse. Then again it may be the output chain, headphones, speakers, cables, mixers, processors, levels, amps, etc....
Going from analog to digital was a big thing for me and still is rather complex and daunting for even the minimum. At this point, I'm only shooting for recording dry and high level tracks to be mixed and mastered by a pro, somewhere else. I'm only using my home studio for tuning up the sources and practicing recording and practicing my listening. I can only afford so much quality.
You'll definitely find the info you need on this bbs, it's awesome.