Having repaired/built guitar amps for nearly a decade now (among other interests!), everything in DCC sound land seems so feeble and insect-like! A 130w Fender Twin hooked up to a quadbox (4x 12" diameter speakers) at full-bore is real power....
Jordan, are you mounting the speakers facing up within a hood or facing down in the fuel tank as many HO locomotives seem to do? I'd really love to see an O-scale loco setup with a multi-channel sound system - small, 'bright' horn speakers at each end, a low-end rumble sound from below (also for track noise) and a higher-end turbo whistle from above, mounted near radiator fans. Give it a few years, I'm sure that'll be the next frontier..........