Another reason why I love my m-audio fw410 interface...2 sweet preamps on board!!!
The Shure Beta 57A is like the SM57 on crack. The range is wider than the SM57. It not only mics instruments and amps well, but far exceeds the SM57 on vocals too. If money is tight and you really need one good, multi-purpose mic, then I cannot think of one better.
Also, there's a sale at americanmusical.com on Marshall V57M Studio Condenser microphones for 59.99!!! It's a blow out sale and they originally sold for high $300's!!! Comes with shockmount too.
Check em out: http://www.americanmusical.com/item--i-MAS-V57MMIC.html
I bought one 8 weeks ago and use it to mic my wife's cello and it does a great job on vocals.