Do you know that the 8x10 you ran it through at practice is good?
Assuming it is, then the issue is definitely not in the speaker. That leaves the amp, cords, and instrument.
Test each one with known good replacements. Many times amp issues have turned out to be bad cords.
Once you've proved that it's the amp (assuming it works out that way), then you'll need to find a tech. I'm in Oregon, so I can't help you there.