The ART Tube MP is the only pre I have that cost less than 50, and that's cause I got it dirt cheap of a guy used locally, and he only threw it in cheap cause I bought his snare...
I agree, go with a Tube MP if you absolutely can't afford more. These things aren't great, but they aren't bad either. I have super expensive mic pre's, and I still pull out the old Tube MP from time to time to dirty something up by overdriving it. Granted, I use it for more effect than anything. However, I bought mine when they first came out, and I used it on quite a few recordings to good effect. I think they sound better than most Mackie mic preamps.