I used to always use a Celestion Heritage 30 (older, British made, not the new re-issue) or Mojotone BV-30H speaker.
I recently put a Mesa/Celestion MC-90 Black Shadow in mine and it really came to life!
My DC-3 is nowhere near stock though, it has a full set of Mercury Magnetics transformers and a choke, plus a plethora of mods......
For tubes, I am currently using the Doug's Tubes cocktail. Tung-Sol, Penta, JJ mixture. With an NOS US made 12AX7 in V4 (really makes the clean channel shine!), and JJ EL84 power tubes.
I recently got a set of power tubes from Tube Depot and forgot to order them within Mesa spec. They say "24" on them. When I popped them in and measured the bias, it was at about 92ma per tube!!!!!! I immediately had to adjust the bias or bury the amp under hundreds of feet of concrete to prevent a major catastrophe. :shock: