Aren't most residential floors rated at about 50 lbs./sq. ft.? I've seen
folks assemble a platform with 2x4s and some heavy plywood to distribute
the weight of heavy items over a broad area. What are the joists under
your floor like now? I've got 2x12" glue-lam beams under mine and it seems
to be pretty sturdy.
Cheers,
Chuck