You should get both the Shure SM58 and the Rode NT1A. An NT2A will run you about $399.00. The NT1A is a great condenser and costs $229.00. Everyone should have a SM58 in their studio anyways and it does a nice job on vocals plus it's a great stage mic. I go back and forth between the 58 and NT1A recording my vocals. It just depends on the song and how bad I'm singing that day.

You can get both for $329.00 which gives you more utility than just getting an NT2A. I'm sure the NT2A is a better condenser than NT1A but I seriously don't think it's $170.00 better.

For the record I have an SM57 also and have used it on vocals but the 58 handles vocals better (IMO).