Let me get this straight, you have a hard-panelled 20'x30'x16' room and you even consider using artificial reverb?!? What is wrong with this picture?
Beg, borrow, or rent a good omni condenser mic and use it for the "effects" on everything. Play around with placement until you find a spot which works.
Definately mic the amps at least 2' away (possibly combined with a 57 on the grill.)
Natural space is what separates great studio recordings from 'home' studio recordings. You have the space, please use it.
BTW There's nothing wrong with a 57 on vocals. They don't have quite the 'presence' of a 58, and you won't get the brilliance and detail of a top condenser mic. But, I know quite a few male blues singers who sound excellent with a 57.

"Take 276, you know this used to be fun."
John Entwistle