Some quick advice
Hi!
Just a couple of questions. What interface and DAW are you using to record your amp? Is there anything in your signal chain before the amp? What type of guitar are you using? How long is the cable between it and your amp and how long is the cable between your 57 and the interface?
Also, what about the sound of the 57 don't you like? The reason I ask is because a couple of the mics mentioned in this thread will share certain characteristics with the 57. Any condenser mic you use will tend to bring out the low end of the amp, but also they will sharpen the highs quite a bit (just the nature of the mic). Another thing to consider; what kind of speakers are you listening to your recording through?
All of this is to say, the specific problem you're experiencing with your 57 may not be the 57 at all. I've used Crate amps and best amp in the world or not, they sound pretty decent. However, if the quality of the 57 that you don't like is the muffled sort of 'muddy' quality the crate amp might be emphasizing this as they tend to be voiced more toward the chunky metal rhythm side of the spectrum.
A final note, if you do end up getting a new mic (particularly a ribbon mic) DON"T throw the 57 totally out of your arsenal. Ribbon mics can make your mids and high mids awful screechy without a nice mellow dynamic mic (like the 57) to even them out.
Happy recording!
-Tim