Speakers

I would just keep an eye out on craigslist or the like and you probably can pick up a pair for practically nothing just to give it a try.  Again, I wouldn't have mentioned it but they just blended together perfectly.

Great receiver!  The Sansui does a credible synthetic quad surround sound, so I would go with four loudspeakers.  I think you should consider some vintage Klipsch loudspeakers, the KG4, Forte or even the Heresy.  Good luck!

What does one look for/worry about if buying old/vintage speakers?

Jbl l80 or higher. That's my solution for everything. 

I have a pair of speakers that I bought new in the late 70's. Used them lightly for a few years with a Pioneer receiver. They have been sitting unused for a number of years. Synergistics is a brand that I never hear mentioned in these forums. But, in the day, they gave brands like JBL and others some competition.
The unused speakers should go to someone wanting good sound and not to one who only wants a nice looking speaker for some background music. Just don't have the heart to dump them at a garage sale. They are in good working order and still look very good cosmetically.

If anyone is interested in these speakers they are free of charge. I would only ask to be reimbursed for the shipping charge since they weigh about 50 lbs. each. Here is a description of the speakers but they aren't mine. Just photos I found online of ones belonging to someone else........
http://www.jlaforums.com/viewtopic.php?t=212689171