BuyDig offers the Beyerdynamic Headphone Amplifier for $499. Coupon code "c1176207331" cuts it to $299. With free shipping, that's tied with our February mention and the lowest price we could find today by $51. It features an ALPS potentiometer volume control, high-gain RCA input, hard-wired RCA output, two stereo 1/4" headphone outputs, and 10Hz to 100kHz frequency response range.