Hello, I am considering getting a Trace AH150SM, I have a Trace 1518(1 x 15 cab 300 watts) The AH150SM has a 4 ohm output impedance(150 watts). The cab is 8 ohms. Would it be safe to run just the one 8 ohm cab. or do I need two 8 ohm cabs. Also,is 150 WattsRMS loud enough. I play in a loud rock band and I like to have some headroom.