This is one great little combo. Also very good for recording thanks to the XLR output and the Sansamp circuit. I do all my demos with it.
I don't have the schematic and although I am sure that the signal going to the PA can be increased, the circuit is pretty much all SMD and therefore not modder-friendly. However, there are several alternatives that can help you reach your goal:
_ you can use the FX loop output to drive an additional guitar amp (through its PA in or FX loop return). I did this once for a gig in a 1000 seater and it worked great.
_ you can plug into the PA using the XLR out of the TM10 (with the speaker simulation NOT off). It sounds very, very good, if you engage the low cut filter of the mixer's channel,
_ you could also use an alternate enclosure with high efficiency speakers (Vintage 30s, centurys or others). I use mine like that.
You will have to more or less modify your tone settings in all cases but it should work well. Hope this helps!