My initial and follow-up posts deal with this earlier in the thread.
In Short:
My DB750 will be for sale in the next month or so. The STL900, while by no means a clone of the DB750, accomplishes the same things: tube warmth in the pre, solid fat lowend with a slight sag ala a real tube power amp, and silky non-abrasive highs.
And yet it adds in light weight, tighter bottom end overall, and a much more flexible EQ section. Between the gain/volume/master volume and the midrange EQ, there's literally several very different tones in this amp that would satisfy just about anybody.
The ONLY challange in this IMO is that you need to write down your preferred settings in achieving different tones. Every turn of the knob makes discernable changes. I've pretty much settled on the following:
Gain and Volume at 12 O'Clock
Bass at 10 O'Clock
Midrange at 2 O'clock with the 220hz setting selected
Treble at 12 O'clock
Master Volume at 10 O'clock
With my two Sadowsky Basses (PJ5 with heavy flats, JJ-style 5 with Rounds) and through my Accugroove Tri115L's, I"m getting a full range tone with a low-mid kick that makes me giggle maniacally.