Watch the Dickey Betts online guitar lesson by Jeff McErlain from Kings of Tone
Dickey's classic amp setup is pretty straight forward, a Marshall 1987x 50 watt plexi through a Marshall 4x12 cab loaded with JBL speakers. My understanding is that he switched to the JBL speakers other than the usual Celestion speakers because the high wattage JBL's lasted longer on the road. So as a result they became a large part of his sound. Speakers do play a huge part in the tone equation, if you get a chance try your amp through a number of different speakers and cabinets, you will be amazed at the difference.