Harman Audio offers the factory-refurbished JBL 50-watt 4-Channel Car Amplifier, model no. GTO-504EZ, for $139.99. Coupon code "99GTO504" cuts it to $99. With free shipping, that's $41 off list and the lowest total price we could find. It features set-up CD, and built-in variable electronic crossovers and variable bass boost. A 1-year Harman Audio warranty applies.