Pulling the trigger on pricey equipment

I would agree with Bifwynne - exchange telephone #s & call the seller. Have an extended chat with him. It will give you a feel for the person.
Like Bifwynne, I've been very lucky in my sales & purchases on A'gon but each time I called the person & chatted with them. That always gave me either a good feeling (yes, I want to buy from/sell to this person) or a bad feeling (no, this sale is not happening with this person).
Your angst is very understanding & many of us empathize. All the best....

If I was buying gear which was more than a few hundred dollars, especially if several (or more) thousands, I'd drive/fly to the seller's and meet in person to see/touch/hear the gear first. Less risk once the seller knows you not only know where they live, but are also willing to pay them a personal visit, if necessary.

Be patient and wait for the item to be available within driving distance. I drove halfway to Maryland from Jersey for my speakers.

What about using Facetime. That way you get the meet the seller... and actually see the equipment you're buying.

I think everyone who uses Audiogon shares and empathizes with your concerns. Fortunately, I have had only enjoyable transactions here but it does take a degree of luck and almost a second sense about the party on the other end of the transaction. The most important thing is to try to strike up a conversation with the party you will be transacting with, both through e-mails and on the phone and follow your instincts. I can think of a few occasion's where I was interest in purchasing something and the response just put me off and made me wary. Obviously, in those cases I just drop it. Not worth the risk, and indeed there is a risk factor. On the other hand, it provides you with the opportunity of putting together a system of a caliber you might otherwise not be able to afford to.