I went from using Hartke heads for many years, to a Streamliner. I now have an amazing rich valve tone and way more low end on tap than I ever had before. (I was using Ashdown cabs which did the job just fine, but in the past year I've moved to Bergs, and they're stunning with my Streamliner.) You really need to try a few Genz amps out, you have to hear them in the flesh. The Shuttles are fab too, I just prefered the simpler Streamliner myself, but try them both out if you can. I suggest a visit to Bass Direct. And, the prices are a steal at the mo....