nad is notoriously unreliable, although the 80s stuff you list is much less finicky than their later gear and also sounds good. the amp and preamp seem to go for $200-$220 each on ebay and the tuner for $50-60; depending on condition and whether you save on shipping $575 for the set seems like a fair (but not great) deal.
Purchasing barely used NAD gear
I have the option to purchase some used NAD gear. $575 Lightly used and hasn't been used in 25 years. What kind of issues might I expect to encounter with gear this age. It looks brand new. I'm not as tech savvy as some of you fine folks! Stereo Preamplifier 1155, Stereo Power Amplifier 2200 Power Envelope, Stereo Tuner 4130