Adcom - A Good Value?? Auctions risky??

I really have 2 questions.

First, There is a lot of discussuion here and elsewhere that make Adcom sound pretty bad. I am looking for a good amp with 200+/chanel and good down to 4ohms, without breaking the bank. The old 555 may have been rough, but how about the 5500, 5800, and 5802?? The 5800 would appear to be a pretty good deal on the surface, at around $600 used. But some have raised concerns about mechanical noise and noisy fans. Has this been a significant problem for any users?? The 5500 and 5802 are current models and seem to sell about $900 and $1400 new. I have seen the 5500 at about $600 or so used. This is no less than a used 5800, which would seem to be a better value, unless noise is a common problem. It appears the 5500 and 5802 have no fans. Do they have no noise problems? If the 5802 is the best of these might it be best to wait for the next generation to come out so the 5802 will then drop to say $800?

Second question is how risky is buying an amp over audiogon or ebay classifieds? If you get a DOA or even a hummer you have little recourse but complaining. I am sure there are horror stories. Is the experience generally good, or is this just a gamble?

Thanks in advance for thoughtful reactions!!!!

Steveg