+1 on the e609. i like it in conjunction with my Dragonfly. Those two make for a KILLER guitar track out of my Vox Pathfinder. pan wide and stand back!
The sennheiser e835 is also a nice change from the 57.....for the same reasons they make a nice contrast to the sm58 on vocals.
FWIW, i prefer the older shure unidyneIII 545 to the sm57.....and i prefer the US-made ones at that. the 545 is essentially the predecessor to the sm57.
the 57 also benefits from a higher quality preamp, and i've found that having impedence switching (loading) on the preamp can make a large difference in the sound of the 57 as well. i noticed this "improvement" using my VTB-1 one day, of all things.
a sleeper mic that seems to be pretty rare around these parts (and also not under $100) that i LOVE on amps is an EV RE38. it's a large diaphragm dynamic. in fact, i've found very little that that mic doesn't excel at--it's prolly one of my favorite mics, and is supposedly a cousin of the RE20. it too has different tonal characteristics depending on the loading.
cheers,
wade