The 609 silvers are pretty good, smoother & fuller then an SM57 which always sound 'peaky' to me. But really...
any mic can be good for recording guitar amps. The bigger varible is placement, a $3K mic in a bad spot will sound worse then a $100 mic in a great spot.
BTW...this is a great book for the basics of recording;
http://www.amazon.com/gp/product/02...103-7224533-2557441?s=books&v=glance&n=283155
People I know who went to college for "production" were handed that book and it's pretty comprehensive. I found it on my own and saved a few thousand bucks! It'll tell you everything you ever wanted to know and even some stuff that you didn't.