Well, the 4033 is such a versatile mic, I think you made a good choice. After reading the thread I mentioned, I'd like to hear what the SM 57 sounds like on the banjo. It might be real cool for that application.
If I was you, recording bluegrass, I'd pick up a couple small diaphragm condensers--either the Oktava 012's or a par of the MXL 603's. They are supposed to be damn close to each other in sound quality. I also liked Harvey's suggestion of the ECM 8000 on the bass. You can get one of those for under $40 bucks so thats a no-brainer there!
Are you doing this as a one man band, or are there other musicians coming over?