I feel the Streamliner is one of the most complicated amps on the market. The Max 9.2 with all those knobs... simple as pie. The Streamliner, with everything interacting... gain, volume, midrange, bass control, etc., etc., it can get a bit crazy. It is worth the time to really get to know it IMO and IME, but it is not a 'take it out of the box, plug it in, and play' sort of amp. And, IMO, just like many all tube amps, it seems quite sensitive to cab matching, and can sound wonderful, or a bit flubby depending on the cab, no matter how you turn the knobs.
Good luck. Don't be afraid to really twist those tone knobs, and don't be afraid to really experiment with different gain levels and gain/volume ratios, with and without the boost.
I've had an STL 600 for over 5 years. It's the best amp I've ever used.
Yes, it took me a month's worth of gigs to figure it out, even going back to my former amp (Hartke Kickback) out of frustration initially (before that a full Eden WT-800 and XLT 4x10). Amazing but bulky and heavy), but once I was able to understand the sensitive controls, my basses sounded better than ever and I have not looked back since!
I use a Bergantino HT112 that adds hi-fi clarity with the tube warmth of the STL. My P-Bass sounds incredible, my 6 String Anaconda Bass sounds fantastic, the low B absolutely immense and my Crafter Acoustic Fretless sounds beautifully warm.
Unfortunately, it's not as simple as 'put everything at 12 o'clock'. Speaking in 2021, it's still my go-to amp. I'm not convinced the Genzler Magellan truly captures the essence of the STL without any tubes. If anyone has had a chance the A/B the two, I'd love hear about the results.
If anyone's interested, I can post a photo of my settings.