a couple of PERSONAL observations now on the V6 vs. SVT vs. solid state thing: this is just for haha's and gear chat, not the opinion of the "Genz Benz Product Manager".
Tube amps- well, if I were to go back to these I would go back to 10" speakers vs. 12"s. They seem to tighten up some of the sub-tone-woof that I hear in tube amps. I would also go with a "modern" cab design. I played both these amps through some well respected, major brand cabs that weren't "modern" and man, did it sound woofy.
Tube amps again- I'm still more of a solid state guy because of my style but I do have to tell you, both the SVT and V6 do something "special" for fretless- a real nice growl and warmth...complex mids.
SVT- what can you say...it's a classic. For both slap (Lull MV4 with barts and aggie three band) I had to EQ more than I like but once there, very nice.
V6- I was able to get my tone with everything straight up at 12:00. For whatever reason, I always like that.
SVT vs. V6: The V6 is supposed to be 600 watts but it didn't seem any louder then the 300 watts of the SVT.....head room included. Also on the V6, the deep switch sounded really like a mid-scoop so I found it unusable. Then again, the V6 has so much more bottom end, I didn't need it. Again, with the V6, I didn't find the push/pull mid voicing useable but again, I didn't need it. MAN, THE V6 RUNS HOT!!!!!!! Lastly, did I mention that THE V6 RUNS HOT?????
With the SVT I really liked that I can't get a tone that is "too over the top".....can't really find a bad tone in it. I find the rotary mid voicing very usuable. I really dug my fretless (Zon Sonus 6 string) through it. I did find myself boosting lows for slap with the fretted though....boosted them quite a bit but, the "extra bass" switch I found very useable for this. MAN, THE SVT IS HEAVY!!!!!!!!!
side note: I messed around with running both amps through THD HotPlates so I could crank them. Man, that is fun. Not "my" sound but I definetly plan on using it on some recordings here and there for effect.