I think a fine second system can be built around a vintage receiver. Keep in mind, though, that they are more likely to have problems due to parts aging. If you're going this route for bang for the buck, you can just wing it and hope for the best. The risk is that a power supply failure could go either way - it won't power up, or it could take out your speakers.
However, if you plan to maintain a vintage system, you should consider getting an estimate for a parts refresh. Jon Soderberg at https://vintageamprepair.net might work on Nak receivers. He worked at Threshold, so he's quite familiar with the Stasis design. I'm sure others here can recommend other reputable technicians.
Considering you mentioned hooking them up to Quads, though, you might want to up-budget for separates. Hopefully, tuners are a buyer's market, at least... Another classic speaker that should work superbly in a bedroom system would be the LS3/5A design.