I know this thread is really old, but for anyone newly reading this and looking for ideas I have a slightly different suggestion.
I've recorded entire cd's (the kind you can buy of local indie artists in the indie section of major music stores) using a soundblaster (16 bit stereo), one radio shack cardoid electret condensor microphone, lots of $4 radio shack cable adapters, and sonar. But then when I did that I was already a pro musician and pro engineer but I just had no cash and was doing somebody a favour for free. The sound quality was fantastic and I had a lot of shocked looks from pro engineers in some local pro studios (many of whom I'd never met before) who were impressed with the tracks and often thought it was done in a pro ANALOG studio. My point is simply that you can do great things with very little hardware if you know what your doing AND you take the time to experiment and get the most out of what you have. My one $25 AA battery powered microphone is incredible sounding to this day (I still pull it out for lead vocals on certain singers compared to the akg tube mic I rent regularly and shure, sennheiser, Apex and AT mics I own). So I think personally that a great sounding mic (even with poor quality construction like my radio shack toy) and a good understanding of setting levels, micing voices and gear properly and mixing properly are all the basics you need to record great. If you have crap sounding mics, that to me is the most obvious thing you can upgrade. The mixer will affect the sound a bit, but not obviously compared to your mics. the soundcard can affect the sound subtly if you're already using it very well, although a better soundcard is more forgiving of your mistakes so could make big improvements to your recordings if you're not a very experienced engineer or haven't just worked out how to get the best sound possible from your existing soundblaster.
I'd go mics first (cheap apex 435s, $55 per mic in canada, 1" LDC cardoid mics that sound great for drums and often really good on vocals with a bit of eq). get a handful of those with phantom power on your mixer, you'll upgrade your sound a lot for cheap (cheaper than sm57s and more of a hifi sound which will help beginners get great mixes with less trouble I think - not necessarily better mics than sm57s, just sort of pre-eqed mics which have their advantages and disadvantages).
Then I'd go with a 1010lt (I just picked up another of these for $120 US brand new old stock private deal, so you can get 'em cheap if you shop around and they sync well with multi 1010cards in your machine for crazy numbers of inputs and they're compatible with not only all pc and mac software but also with protools m-powered!).
Then I'd get a new mixer, one with lots of mic eqs, and personally I'd make it a high quality used mixer rather than a new behringer or yamaha, but that's just personal preference. No matter what, for beginners you can't go wrong with yamaha mixers and other yammie gear, so it's a safe bet at least, used or new.
But first and formost, before spending any more money, I'd try to make a full mixed song using the gear you have that sounds as good as your favorite commercial song. Tune and eq every tone you record to sound as much like the instruments in the commercial track so you improve your final sound and learn in the process. Also level setting and compression are vital to making a great mix. And a note for all beginners, dont' go crazy with reverb or other effects - it muddies your mix. Spend more time getting great levels, less time covering problems with reverb. I haven't listened to your tracks so this isn't directed at you in particular my friend! Just a note for other new users looking to upgrade hardware - always upgrade your ears, experience and knowledge first, then your hardware can be upgraded to match your new skills.
Cheers,
Don
