Congratulations for your new "toy"!
I hope you will be happy with it.
I attached two videos at the end, but first read the info below. Thanks!
Well, your story reminds me very much of my experience when I got the DC-3 a couple of months ago: second or may be third hand, very dull, lifeless, harsh sounding amp at the beginning. I was very, very disappointed, HOLY CRAP, it is MESA, it should be brilliant!
Then I changed all the tubes withh JJ's bought from http://www.eurotubes.com Great services from those guys, and most important, as everybody says, the best for Mesa are the JJ Tesla. Period. When I put the new set of tubes the tone improved for sure, but still dull and with no so much punch and life. Then I read in some topic here about bad solder connections of the tube pins to the board. Well I decided to open the amp. Man, yes, I was expecting to find some imperfections, but can you believe me? What I saw was every single pin connection of the four EL84s in bad situation. I suppose this was due to the high temperature of this amp when it is working. I installed a cooling fan now, and I am happy with the results. No more melting chassis.
Then I grab the soldering tools and resoldered carefully everything there. Talking about change? A HUGE one, man! This amp finally became to live.
Unfortunately, I can not say I am 100% happy with my DC-3, I am trying to find if the sound now is the original Boogie or something else is still bad. It is all because, while the amp now is punchy, with character/life, much more clearer and adjustable, it is still lacking some things, such as bottom end punch of my ENGL Screamer (previous amp), for example, some more presence that the ENGL's had which is awful when you play alone but is just AMAZING when you play in a band. The DC-3 is the opposite: sounds outstanding alone, but is just lacking character in the mix.
http://vids.myspace.com/index.cfm?fuseaction=vids.individual&VideoID=57572455 (Mesa Boogie DC-3 prior to the service - old tubes, bad connections)
http://www.youtube.com/watch?v=8-LyHjzUycI (ENGL Screamer - one of the few times in my life when I was really happy with my sound on stage, just missing that tone, MESA DC-3 could not give it to me till this moment)