Well mosfet is used for being more stable and faster switching power supply than previous amp generation. The mosfet IC is small yet power pack. Look at pioneer use it widely ever since it release it. Monoblock amp best suit for subwoofer as it churn out more watts at low thd level. Thd stands for total harmonic distortion. The lower the rate per channel watt output the higher the amp quality. Take a comparison between soundstream Xstream and Picasso. Picasso give out more cleaner and lower distortion than xstream.