Yeah I'm a fan of SM57's and SM58's for playing live. For recording vocals and acoustic guitars I'd recommend a $100-$200 condenser mic of any brand really. The thing is, you need a phantom power XLR connection. Dont know if your audio interface is equipped but its definately possible.
Condenser mics for vocals are just so crystal clear and warm. Same with picking up acoustic guitars as well. Definately what youre looking for when recording "delicate" types of clean, undistorted instruments.
This is the one I use for vocals. It actually comes with a free cheap little pencil condenser mic so you can mic the bridge of the guitar and use the big boy for vocals at the same time. Havent tried it, but the pencil mic works good for snare drums.
http://www.musiciansfriend.com/pro-audio/mxl-4000-multi-pattern-fet-studio-condenser-microphone
