+1 for the prior post in getting comparative quotes from branded reputable couriers , but with the express understanding that that they are PROPERLY prepared for shipment FIRST to avoid tragedy .
Do you still have the original OEM boxes and (presumed) shipping crates and other packing materials (Y/N) ?
if not, I would heartily recommend that you first contact the speaker distributor and order up & pay for the OEM replacements as a cheap cost of insurance and peace of mind against getting them banged up and damaged during delivery.
They are going to be crated and likely also secured to a pallet because of their extreme size and weight, just even to get them properly insured for transit
There is no cheap short-cut here, so it is going to be unavoidably comparatively expensive.
Or else ....... full stop.