Also I found this thread interesting on the V4B, but maybe you've read it already :
http://www.talkbass.com/forum/f15/ampeg-v4-b-any-mods-make-more-output-625713/index4.html
http://www.talkbass.com/forum/f15/ampeg-v4-b-any-mods-make-more-output-625713/index4.html