Well, I don't really mean "versus".. But I'm curious---- Since I am enamored with the tone of my new V4BH- What are the differences between the older Ampegs, the SVT's V4,s etc. and the current line? I'm referring to actual differences in the circuitry that voice the amps differently. I was under the impression, that except for cosmetics, the tube circuits were the same-if so why is there an opinion that vintage SVT's are louder, stronger, whatever. Same w/ the B-15R- I know they added atweeter/midrange, and it's higher powered, so there must be some re-design there. Anybody know? How about Psycho-Bass Guy? I know that you are an encyclopedia re: tubes. What has SLM done differently?