I not a massive fan of ashdown, but they do seem to be everywhere! The standard set up in almost any rehearsal room around Glasgow seems to be the ABM Evo II 500 head/ampeg svt 450 on top of an ampeg 8x10.
I don't really have a preference between the Ashdown and the 'faux' SVT. My view is that the Ashdown is great for plugging in a passive P-bass going through a Sansamp and a bunch of fuzz pedals, but if you use a clean high powered active bass, the Ashdown doesn't really provide much top-end sparkle. Even trying to fiddle with the eq seemed to make little difference.
The sub octave thing isn't really for me and just seems to muddy the sound, unless you are playing around the 12th fret on the D and G strings, which provides a sound very much like playing around the 7th fret on the A and D strings. Thus, I don't see the point. Also, the valve drive seems to be so sublte that it makes minimal difference to your actual sound, so I have yet to fully appreciate 'grind'... Furthermore, the dial thing on the front is to me superfluous. I don't believe they are as accurate as they would seem. Several times the amp has cut out on me after being apparently being driven too hard, even though I've had the master volume below half and the gain turned up so far that the dial was almost getting halfway up when I was digging in. That may have just been bad luck with a faulty amp but I still think an LED or two works just as well, if not better due to ease of operation, as an indication of gain settings. Also, why have an active/passive pad if the dial is there to let you easily dial in a sufficient amount of gain. I'm a novice in electronics though, so somebody could correct me on that.
Its these aforementioned things that just make me think the amps are just a bit gimmiky, which lots of knobs and buttons that make little difference to the sound. They run a brilliant marketing campaign, but I personally consider the ABM Ashdown amps to be a step backwards from Trace Elliot (well, the Kamen stuff, not necessariliy the Gibson-era).
I will say that I have not tried the US series valve amp which admittedly does look kinda cool, as well as the Little Giant etc. The MAG stuff also seems to be decent value for money. Hell, compared to the stuff from the US and Europe, you could even argue that the ABM stuff is value for money. I just wouldn't buy it unless I knew I was going to spend the rest of my bass playing days running my P-bass into a Sansamp Bassdriver or VT Bass. It would be fun and it would sound pretty good, but its not really what I want to do.