On Order. 45 Day Lowest Price - 100% Satisfaction Guarantee. 125 Watt, 1x15" Rock Back Combo, Clean+Distorion Channels. The Backline Combo Series puts GK sound in its most affordable package ever, making it accessible to many more players. The Backline is essentially the 400RB design with the distortion circuit featured in the 2001RB. You can get the same natural sustain and growl from the Backline as the touring bands get from their 2001RBs.