I'm giving away a secret that anyone would have figured out anyway, so what the heck. If I feel like playing my Deluxe Reverb and I want to do 'medium size' gigs, I replace the speaker with a Red Fang. A little tweaking to the circuitry, and I have a giant killer that can hang with loud drummers. Remember this, and I'll come back to it in a second. If I have a Twin Reverb mood, and the band usually bitches how loud it is, I replace the speakers with a Jensen Mod 50. Now for the science and math.
A 3dB increase or decrease in speaker efficiency will give the apparent effect of doubling or halving the power to that speaker. As one example, a 50-watt amplifier with a speaker rated for 99dB and a 100-watt amplifier with a speaker rated for 96 dB will appear to have excactly the same volume. It's not magic or abstract math. Still with me? The stock P12R in a Deluxe is rated for 95dB, which is actually not so hot. The Eminence Red Fang is rated for 103dB. You do the math. Without too much BS'ing, a Deluxe with a Red Fang can hang with some 50-watt Marshalls. The C12K's in your Twin are rated for 99dB, which ain't too shabby. However, to tame some excessive volume, I use the 94dB Mod 50's. You have just enough power handling, so be careful. But the huge loss in SPL's means you can turn it up a little to get some grind and not get complaints from the rest of the band.
That's how I do it when the situation warrants, but feel free to disagree with everything I've just said.