Mesa 400 with a roadready cab, the stock speakers were replaced with JBL D-140. I have a thing for that JBL sound, but I am afraid the 400 is pushing then too hard. It seems to fart way too fast, long before I get to the "I'm going deaf here" volume. I have not toyed with the amp yet, the guy I got it from said he had it "biased cold" to save tubes, so I know I have to get that looked at. 2 things I'm thinking: the bias is way off and I'm hearing the amp run out of gas or the D-140s won't take it. also: does getting rid of the 6L6s and replacing with 6550s make a substanial difference. Bass is a Rick 4003, music is blues, rock, classic rock. Would love the sound of my old Marshall Plexi with 2 Sunn 200s cabs. I thought this would do it, and it is really close, just not as loud as I would have thought.... or I have gone deaf, always a possiblity. Thanks for any input guys!!