Mike
Build a pair of crates the same as the HT8 crates you now have

Use the same materials we use 2x2 with 3/8 or 1/2" plywood.
Screws every 6" and the screws must have a shoulder not a wood screw they will pull threw.
Line the crate with 2" solid foam all around leaving another 1.5" for a soft wrap like bubble wrap to cover the speakers.
So when you open them up you have the crate,2" foam walls inside and then the cabinets wrapped in bubble wrap.
And last the cabinets before the bubble wrap a fabric sock.Just like a sono tube sock

.This will stop minor scratches while handling them.
The rest make them as bullet proof as possible, sit back look at them and if you think they are week packing materials in anyway .You will be correct.
WE have learned the hard way.DO NOT SHIP VIA UPS OR FEDEX even freight with them.The handling does not change.Use a freight company and put them on a pallet.Make not for pick up and delivery they will need a tail gate and payment will need to be arranged to have them put them in the garage of the delivery location if that is a option.
Next take pictures of the complete packing materials during the time you pack them up right till they are ready for pick up.
With this then no shipper will be able to make comment they were not packed correctly, you have the proof.
Last Mike INSURE them.
Did I say we do this from time to time aa
The worst, we even had afreight company drive a fork lift into the side of a pair of Apex II.Lucky for all the compression as they were fine.