This sounds like a very serious and dangerous problem.
I do not know how resistant fire ants are to poisons,
but I suspect that you will have a difficult time
finding poisons strong enough to kill most (but not all)
the ants, and which won't kill your plants.`
I don't know if fire ants act like other ants, but if
they do, submerging the pots should kill many of them,
and cause the rest to move out with their eggs. I'd
probably use a heavy duty pesticide on the ant trails
both before and after treatment, for as they said in
Aliens "It's the only way to be sure." Also consider
that if the little buggers DO move out, they might move
closer to your home.
IMHO, fire ants seem to be a much more serious danger
than "killer bees".
Robert