Sorry for your troubles OP. Personally, I've had lots of good experiences on USAM. I prefer to do local buy/sell using cash only. But, We are not talking high dollar items here. The most was my Hegel h360 that I paid $2,600 for a few years ago. Met the guy in a busy mall parking lot. There have been a few flakes and tire kickers but mostly serious 'philes. Met quite a few nice guys and checked out their systems as a bonus. Maybe I've just been lucky?
Of course, never give any info/address until properly vetting. A phone call is a must. Best of luck!