I'm not at all as experienced in busking as some like alanabit and Reggie and, in general, tend towards preferring the unamplified.

However a small amp (like the 10W Fender) can be useful if busking with a quiet instrument and I am very sympathetic to such performers. Recently, in Berlin, I got into an interesting conversation with a young Russian girl busker playing the domra quite beautifully. Being a quiet instrument, it did definitely benefit from a little amplification through a battery powered amp she had.

On the other hand, we have a busking group here in Brussels in the same spot for several hours every Saturday with a state-of-the-art Electrovoice mobile PA and, I must admit, I quietly utter more than one rude word to myself as I pass by!

Peace,

moo