#2
What mixer do you have? Because if it isn't a 'powered mixer' you're going to need either an external power amp, or to look at different (active) speakers.

Also, as a general rule Behringer quality control is atrocious and so I can't imagine their speakers are much cop. Look for second hand Mackie SRM's, they should be affordable if you're lucky.
Hey, look. Sigs are back.