Well, since you can afford the Eidolon Diamonds, I assume money is not too tight for you.
I suggest you do exactly as you stated:
"What about just buying/testing through multiple Audiogon buys? And try not to take much of a loss in the process."
That is what a lot of us do. It provides us with a opportunity to listen for extended periods, (for very little lost, except for shipping), and if you do your research both through the magazines, but here as well as on AudioAsylum, you'll get a pretty good idea of how well the product sounds, so you can put together a fairly small short-list of equipment that should work well with your system.
(FYI, virtually every product will get one, or two, mediocre reviews either here, and/or on AudioAsylum, so don't get too concerned if your favorite short-listed piece of equipment is not raved about by everyone!)
Plus this is a hobby, so trying out different pieces of equipment, (that is until you find just the right one!), is just part of the hobby.
If I can make some recommendations though:
1. The Eidolons (particularly the diamonds) are really great speakers, and the better your equipment is, the better the music will sound. (The sky is the limit with them.) Conversely, if you feed them only average signals, you'll only get average sound out at the end.
2. My friend has the Eidolons, (the regular version), and he discovered, and I agree, that feeding the Eidolons plenty of power is the way to go. (Which for you is okay, since you are not looking towards tubes anyway!)
(FYI: He currently is using the Lamm M2.2 hybrid monoblock amplifiers (220 wpc), and they sound great. (In fact, they sounded so great, that I found a pair of (used) Lamm M2.1s for my Revel Studios, and they sound great with them too!))
3. Don't cheap out using mediocre cables either. The Eidolons will sound only as good as the weakest link. He is using Nordost Valhallas (XLRs) for both his preamp to amp link, as well as for his speaker cables.
Good luck, and have fun searching!