my 01 kia sometimes has a bad power surge when I hit the brakes at night, it cuts off the radio for about 2 sec. and the dash and head lights dims, What could be the problem?

I would check the brake lights ground return; run a new ground wire from rear lights to engine block/battery negative. I'd do the same for headlight ground. ..then report.

The brake light ground return, where is that located? under the dash, or by the brake lights?