I have for sale my modified GK 400RB III. My amp tech upgraded the 240 watt power amp and transformer to the 300 watt power amp and larger transformer from a USA built Backline 600 (NOT a Taiwan or China built one). He also added a Speakon jack. This thing cranks. More watts than a 400RB IV and pretty close to the 350 watt 700RB series 1 head. Lots of the GK Growl. Check out the pictures for more details. I was asking $275, but now only $250 shipped to the CONUS. Message me with any questions or if you want to buy it. Thanks for looking.