Use escrow service to pay for speakers?

PayPal does offer some protection but it's limited to the honesty of the seller.   Google top ten PayPay scams for an eye opener.  Conversations with the seller.  Video calls to view and hear the equipment.  Asking to see the original invoices.   In the end,  if  you get a good feeling, it's still a leap of faith.  Your due diligence will usually tell you if proceeding is the right move.  Best of luck.

Sounds like you're interested in buying from an individual, so that leaves methods like credit cards out. Tough one if it's for substantial money and you can't do a person to person transaction. Sometimes it's best to err on the side of caution if it's a leap of faith you're not comfortable with. Better to lose out on an item than lose all your money.

How much are you willing to wager?

I've bought well into six figures of equipment (not just audio) from individuals over the years and generally pay by wire/F-F/or other fee free method.   Do your own diligence and know that you aren't dealing with a scammer.  It's that easy.   Of course losing "thousands" would not change my life.  But I have saved many thousands in fees.

Don't let horror stories on the internet convince you that everyone is a scammer and you're not smart enough to tell the difference.

Jerry

Its unfortunate the USA doesn't have E-transfers like we do in Canada makes this so much easier than dealing with third party payment systems like PayPal. But in my experience dealing with buyers and seller in the US is to make sure you have a good feeling about the person and demand at a min phone call and preferably video call showing the items being discussed.  Also if they are not on a reputable site with feedback, like here or USA/Canuck audio mart that makes things questionable, I do not consider E-bay a reputable site anymore.,  And not "I joined last week and I have one persons feedback" types.