Based on his reviews it seems like he's a top notch seller. However since the last review was in 2017, he may have gotten out of the game and this is just a one-off sale of his personal preamp. He also may not want to incur additional fees beyond what he's paying for the listing.
The fact that the payment method says escrow.com but the text in his listing states cashier's check only is confusing, so here's what you do. Escrow.com will cost $65 if he agrees with you to let you use it and pay by wire or (believe it or not) check or money order. They hold the funds until he provides tracking information and they see that the package is delivered to you. You have to read their terms but sounds pretty straightforward. You both feel protected, that's what is most important!
I just sold a Conrad Johnson preamp on here yesterday. Within 5 minutes after I accepted the offer, the funds were deposited and available in my PayPal account. There has to be a certain amount of trust in any business transaction, no matter what anyone else here has told you. That goes for any business, anywhere and especially with online transactions. That trust only comes from an individual's comfort level with the opposite party in the transaction and their transparency about the item for purchase as well as any other background info (ie:reviews) that can be obtained before proceeding with the purchase/sale.
My best advice is to be candid with him. You cannot risk a check payment without an intermediary to make sure item is shipped before he receives payment. If he says no, you move on. But don't just walk away without presenting it to him first. If he is truly the top notch seller that his reviews say he is, he will understand and try to work it out with you. Or not. At least you won't have to wonder if you could somehow have changed his mind.
Hope this helps you make your decision.