Just roll the amps (or active bass's) bass knob up a good bit higher and you'll get some preamp tube distortion out of a SVT-II (non-pro) at most any volume level. Mine does anyway.
I've never played a SVT-II pro, but I seriously compared my old SVT-II (non-pro) to a SVT-Classic I once owned.
(the SVT-CL/Classic models are supposed to be just like a II-pro but w/o the EQ section)
At first playing both amps soloed, I actually thought they both sounded fairly similar.
Playing with my bands I just couldn't get comfortable with the CL's tone and was constantly fiddling with diferent gain/master/tone knob settings and combinations trying to find a sound that just simply wasn't there. There seemed to be some strange artifact to its overall sound I just didnt like and couldn't adjust out.
(I admit If I hadn't already been spoiled by my trusty old SVT-II, I probably wouldn't have noticed this issue with my CL)
With my old SVT-II, I pretty much always leave my tone knobs centered, EQ off and just set its volume knob as needed to get the sound and especially the feel I love every time. (besides rolling more bass on at lower volumes)
Here's a link to a bunch of SVT-II non pro threads and posts. If you haven't read these already, you should take some time and read through em before you decide:
http://www.google.com/custom?domain...;S:http://www.talkbass.com;LP:1;FORID:1&hl=en
Here's a couple other threads you should definitely read:
http://www.talkbass.com/forum/showthread.php?t=498035
http://www.talkbass.com/forum/showthread.php?t=452704