One other thought . . . certain mics are more susceptible to picking up bass vibrations. I have some Samson R11s that sound really good, but you can tap the mic stand while one is on it and it makes bass noise.
The SM58 shouldn't do that, but the Peavey might.
There are also some very high-end mics that you can't even use without a sound insulating mic holder.
Hope to see you soon!
DonM