What is the difference between the MD 308 and MD 309 Integrated Amplifiers?

The MD 309 Hybrid-Integrated Amplifier is a no holds barred unit producing 225 watts into a 8 ohm load and 450 watts into a 4 ohm load, the gain is produced by the tubes with 40 transistors producing the current, The MD 309 comes with three digital inputs including a USB port that feeds our World Class 24/192 over sampling DAC. Full function remote is standard.