Mike, speculation based on what I read in the forums is my main tool when considering a purchase, but I was lucky a few years ago when an A'goner loaned me an amp to add to the three amp comparison I was already doing. I had read so many good things about it, but it wasn't until it was in my system that I realized how special and unique it was.
My only reservation in this kind of friendly exchange is shipping. I recently corresponded with a manufacturer and they advised me to take my amp to an authorized local shop because they had seen so many amps damaged in shipping. Luckily, that great little loaner amp was lent to me by a friend in the same area.
I definitely see the advantages to this because even listening parties have their limitations. I think you really need to live with something in order to really know it.