Argh, my beloved GK amp is having problems. It sounds scratchy, isn't getting full power, and is cutting in and out on me. And I've got a gig here. I've got a backup amp, a TE, that is great for most things, but with this band it just doesn't work. I need that GK bite. How does renting a head work? I'm a pauper so what sort of price can I expect for one night?