For interest, I have been using K3 with a Tokyo Hy-Power HL-700B 12DC amp for 3 months. Excellent results, clean switching, close to 200W PEP from 5W drive (using TUNE), with amp in the 400W configuration (where it uses one of the 4 transistor pairs as a pre-amp). I thought the fan somewhat noisy at first, but now don't notice it. Chris VK2LCD