I picked up a few used tube amps over the past year including Blackstar Club 40 and Mesa DC-3. I got them for a bit less than the going price, so that's cool, but the Blackstar started getting microphonic. When buying used tube amps, do you normally go in with the thinking that you may or will retube once you get it? If doing a full retube, you're great deal may no longer be so good. Any thoughts?