I too am pulling out. My Streamliner 600 will be sold this week.
Im loving my MarkBass F1 too much and really dont need two heads.
I have enjoyed my time with my STL600 but i feel im never going to be 100% with it.
Hard to beat the F1/F500 for a clean, even, relatively transparent amplification system. The Streamliner is a different thing, and I again use it for my 'all tube' tone goal with my passive P. For everything else, I prefer other heads.
It again is massively great at what it does IMO, and really does a great job for me when I want the general tone and feel of an all tube signal chain. And, the biggest bonus, unlike those horrible low powered tube heads I owned way back in the day, the tone stays constant at all volume levels... it only grinds when you want it to

As I've posted before, those who possibly think this head is just another in the long line of hybrids (i.e., solid state heads with just a smidge of tube in their tone) will either be pleasantly surprised or extremely disappointed, depending on the tone goal. I again describe this head as what the Mesa MPulse600 should have been!

