I wouldn't pay $6k for an integrated amp regardless of who made it. There are some separate used monoblocks that I would pay $6k for, but then I'd have to upgrade everything in my system from PC/IC/speaker cables, Preamp, Front End, speakers and room treatments. I would budget about $15-20k to get everything set up properly.
Then I would contact a locksmith to get the doors to my house open because my wife would have changed the locks.
That would give me an opportunity to get my system out of the house. Now where to set it up because it won't fit in the car I'll be sleeping in. ;-)
I think the price point for these amps on the used market is right where they belong. In fact, I think they're a good bargain at that price, though I've seen some used 300B tube amps at that price that are REALLY attractive! Some people who haven't heard the amp may get a chance to sample them and flip them right away (if they didn't like it) for a pretty cheap price. Or, some folks may find "better" sounding amps for the same price as these are used. That Creek model for $1500 (the same price as these are going for used) would be a great A/B test.
My recommendation: Judge your ears and not someone else's words. They got you this far.
Regards,
Mark