I've played around with the Streamliner with several different basses (G&L, Warwick, Roscoe, Suhr). The amp sounds very impressive with all of them. My short summary of the head is "wow".
My slightly longer version is that it sounds as close to my own old-school rig (an Alembic F1 preamp into a Crest CA9 power amp) as any of the lightweight heads that I've heard (Genz Benz, TC, MarkBass). The Streamliner is the only one that sounds like it has a 50lb hunk of iron in the power supply. It takes the bass tone and wraps it in warm, round, buttery goodness. The low end is big, round and smooth.
Can you tell I'm a big fan?
I'm obviously disappointed with Ken's experience with this head, but my hat is certainly off to Genz-Benz for doing their usual excellent job at customer service. It's a pity Ken's rule is 2-strikes instead of 3-strikes. Given the sort of gigs he plays (high dollar, no room for error), though, I get it.
I recently did a quick recording session with the head. The signal chain was:
G&L L-2000 -> Streamliner 900 -> UBER Quad Cab -> MXL Genesis Mic
I played the same riff repeatedly while stepping through the various pickup settings on the bass. I did them all with the bass's preamp on. Here's the order you hear in the clip:
Series | Centered
Series | Neck
Series | Bridge
Parallel | Centered
Parallel | Neck
Parallel | Bridge
Single Coil | Centered
Single Coil | Neck
Single Coil | Bridge
Here's the clip with the guitar in the mix:
"L-2000 Clip"
And here's the bass part solo'd:
"L-2000 Clip" (Bass Only)
In person, there's a pretty significant volume difference between the series, parallel and single coil settings. I normalized that out, though, so that one setting didn't sound better than another just because it's louder.