1970's Audio Research Equipment, worth having?

Put me in the ARC camp.   I hear the SP-3 and power amps driving Harry Pearson's maggies and was smitten.

In 1980 I bought a demo SP-6b and D90, driving IMF monitors and stayed happily with these for 10 years until I traded the IMF's for Thiel 3.5's in 1990.  Again I was happy but eventually traded the D90 for a VTL ST-85, a mix of trade-offs.  Eventually I sold the SP-6b when I went to surround sound in the early '90's, but about three years ago bought an old, much used 6a which I had upgraded with new caps and a new tube set.  The magic is back, with an even better bass than the 6b.  I am currently contemplating purchasing a D115mkii to complete my return to ARC.

To answer your question as originally asked, yes older ARC stuff is still good and a great bargain in today's market.  Expect to do some refurbishing, but also expect you will be content for many years.

Harry, FWIW, be sure to hear the D115II before you buy it. I had one with my 'matching' SP10 - it was a disappointing experience. Not the SP10 - I kept it for 30 years, but I found the ARC lacked warmth and maintanence, both biasing and replacing resistors when a tube blew, was a 

Not as familiar with nor have had any direct experience with ARC gear from the 70's but I do have a "soft spot" for their gear from the 80's.  My home's size is the limiting factor, but if that weren't the case, I'd be pulling both my SP-10 mki and SP-11 mki out of storage and swapping them in and out with either my ARC VT100 mkii or a pair of M100 monoblocs. Also not getting a whole lot of use as of late (but at the same time not willing to part with) is a fairly clean SP-8 mkii that has a wonderful phono section and an SP-9 mki that benefited greatly from upgrading the stock EH 6922 tube to a NOS Cca valve.  For my tastes, the SP-8 to SP-11 range was/is the Golden Age of ARC gear.  I've heard the Ref 3 and thought it was a fine line-stage and have heard a 40th Anniversary preamp in a dealers showroom and would love to bring one home for a test spin. 

Haven't experienced too many problems other than the VT100 mkiii arcing after UPS either dropped the box it was shipped in or another box fell onto it. Fortunately UPS insurance covered the factory re-tube and repair otherwise it would have been a costly undertaking.  Costs of re-tubing will eventually be a concern as the VT100 mkiii does drive its 6550's fairly hard.  In that respect, I've come to appreciate the Shindo gear that is my main system in that Ken Shindo designed his gear in a manner that definitely results in longer tube life.  

Best wishes on your quest!