Pulling the trigger on pricey equipment

If you're that concerned, then don't do this sale and wait for the speaker to become available within driving distance so you can make a face to face transaction.

There are 'Escrow' services. The service holds the money and ony pays it when the buyer gets the items.
Usually escrow services charge a fee. and you would have to do due dilligence on picking one both you and the buyer feel safe with.

Any feeling of worry I would hold off and wait for some near enough you can go there.
Paalletizing speakers is a big deal, and the shipping company has to be really great. Any mistakes and you get busted junk.

The most I have spent here is $2,400 and that was delivered by the owner to my home.
I would be pretty worried with a lot more than that floating on a promise cross country.

If you do it, just make sure you are safe.

I paid over $1000 cash for a pair of speakers once. We met in a Barnes and Noble store in a mall, but the speakers were in his car trunk outside. And it was dark. But he was a real gentleman and it worked out.

I paid $8000 cash for a pair of amps once. It was out of my state in his town. We met at his home (so I would know where he lived). The amps were in his car trunk in boxes. He showed me the boxes and we drove to his bank and he deposited the cash. Then we moved the boxes into my car. At least it was broad daylight. Still using those amps now.

Don't know if I'd do this again.

The biggest ticket item I have bought here was 3700.00 for a pair of speakers. The seller had a solid rating and we spoke by phone before concluding the transaction. I paid via PayPal on a Sunday evening and the seller shipped the speakers out the next morning via Fed Ex freight. I received the speakers 4 days later in absolutely perfect condition. I would do it again in a heartbeat.

Do not just look at feedback numbers. Read the comments. Did the seller keep his promises so conscientiously that they merited comment? Did he go out of his way to package securely? Was equipment rated fairly or conservatively? Both equipment ratings would result in the same positive feedback score but might be differentiated in the comments. e.g. "item was as described" "item was better than described".

For example feedback for me frequently mentions the pristine condition of equipment I sell. I have several pairs of white cotton gloves located near my rack. The result is equipment that looks like it just came out of the box. I still tend to underrate due to age. I also ship the same day or one day after receiving payment. I do not get bonus points for that in my rating but it does show up in the comments section.