Integrated Stereo Amplifier A high-powered Integrated Amplifier employing sophisticated differential input discrete amplifier circuitry. The A-R630 MKII amplifier provides up to 2 x 90W of output power and can be used with speakers of between 4Ω and 16Ω impedance. That makes it the perfect amplifier choice, regardless of whether it's to be used with bookshelf monitor speakers or large floorstanding speakers.