is it possible to mod a 100 watt solid state head (in this case a fender 100b) and boost it up to possibly 200 or 300 watts?
well, you could always hook it up to 3-phase power. might have to modify the power connectors though.....................
Add a high efficiency cabinet. You'll get the same DB boost as doubling or tripling power. For example, if you had 1 x 8 ohm driver in and ideal cabinet. And it had 85 DB sensitivity, If you had 9 of them, wired the same 8 ohms, you'd have near 95DB sensitivity. That's the same as taking a 100W amp to 1000W.