I'm looking at an SWR 550 X -- anyone currently using one of these? I have an older SWR Bass 350. Great sounding head...just not a huge amount of power (200 some watts at 8 ohms). It's wonderful for jazz gigs on upright with my Goliath III Jr. 2x10 and for some medium volume blues/rock gigs on electric with my Goliath III 4x10 - especially with a 4 string. However, I just bought an active 5 string and the 350/G III combo lacks headroom -- especially when pumping the low B. Looking for something consistent with my current setup with more power when things heat up. Comments appreciated! Also how's the Octave feature -- is it decent??? Thanks!