This is just my take on the question, but IMO vintage gear is only a good idea if you are willing to get into the nuts and bolts, and also the history, of the hobby.
You need to know nuts and bolts, and a *good* technician, because older gear needs care: preventive maintenance and repair. It may need modification--volume bypass, preamp out etc.--for some setups. Its value depends enormously on condition and condition is not always possible to judge from appearance. You need to know history because the great names in vintage occasionally produced dud models just like today's makers.
For the OP a Dynaco Stereo 70 after servicing comes pretty close to eating up his budget--a restored and/or modded one could go well over it--and he still doesn't have a preamp or interconnect. I would say do some learning and find out if that's where you want to go, but don't make vintage gear your first step in the hobby, especially for a pair of Atoms. There's time enough later for that.