The 400RB-IV is GK's Artist Series head is an efficient 280 watts, it's a powerhouse! This unit comes fully loaded with pro features: toroidal transformer, series 4-band active EQ, extra output devices, sophisticated SOA protection circuits, and a variable speed fan to keep things cool while operating at high output levels. Basically, it has all the primary features found in the other Artist Series amps but without the bi-amping. RRP $1395