FWIW, about a year ago I bought my Parasound HCA 2205A on CL for $400. (originally seller was asking for $500)
The seller claimed it was 5 years old but had no way to substanciate the statement and the amp has a minor scratches on the casing here and there, but none on the faceplate. Also he did not have any receipt of purchase or original manual and packaging.
I asked for an in home test guarantee (paid full money and got "scouts honor promise" to get full refund if anything was not working, plus I knew where the guy lived). When testing at home using the AVR as pre-pro, the amp sounded perfect, zero noize, trigger worked, channel trims worked and no clipping even when I pushed it to ear bleeding SPL, so it made my sig.
PS. I am using it only to drive my Frontstage, AVR still powers side surrounds.