Today only, Monoprice offers its Monoprice 15-watt Bluetooth Hybrid Tube Amplifier / Stereo for $49.99. Coupon code "BIG20" cuts it to $39.99. With free shipping, that's $10 under our mention from a month ago and the lowest price we could find by $60. It features a 20Hz to 20kHz frequency response, tube pre-amp stage, and solid state power amp.