Marantz MD-880's. I have no idea what they'd go for today or if you'd ever find a pair for sale, but from that era I think they were one of the best (especially for the $$$). Not hugely well known, but very highly rated and deservedly so. You'll probably have much more luck finding the JBLs. Or, maybe Dahlquist?
Allison speakers, Advents maybe
2 words - Klipsch Heresy.
Boston Acoustics A200
DCM Time Window
Acoustic Research 98LSI. Made just after your target years (1981-82ish). Four-way speakers with the same driver configuration as the famous AR 9, except the 98LSI had one woofer instead of two. Warm, rich sound, very musical...you can listen to these all day long. Fantastic speakers that show up occasionally and usually for $300 or less. Highly recommended.
Ditto on the Allisons and DCM Time Windows.
Top on my list: Epicure
can't go wrong with Original Advents (earlier than '77) and there are alot of them out there (ebay)
Popular at the time: Kef 105 (probably more than $300)
stacked Advents(2 speakers per channel) are very nice and can be had for $300
I don't know about "best", but I'd put a vote in for Pioneer HPM 100's.
Design Acoustics DA6 was a very interesting design with multiple tweeters. Don't know about availability though.
AR 10pi, 11's, or 12's.
All great, neutral speakers.
I had a pair of Koss cross fire something or other with selectable cross over frequency's. I thought they were great, but the paper woofers lost theri pliancy and that was that, I moved on to Dalquist DQM-9, very nice and then traded them in for a pair of Inifinty rsbII.
If your willing to extend the time frame to the very early 80s then you should definitely listen to the Infinity IRS series. I don't know what you are willing to spend or the size of the speaker you are interested in but the biggest sound I have ever heard were from IRS V. Unfortunately they were the most expensive and are 7 feet tall with separate colunms for the woofers with their own 1000 watt amps and big panels for multple emits and and emims for on both sides. They were Arnie Nudell's ultimate speaker to get a picture an there is a link to vintage infinity if you look. A more reasonable smaller facsimle are the RS1 B mentioned above. The IRS Beta are the next one down in the IRS series which are superb. Below that there are several others but the Beta can be bought for about $4,000 used the giant V's are multiple times as expensive but unreal to this day. You use your own amp to power those through an external "servo control crossover". The top of the Genisis also an Arnie Nudel design are similar but you are talking about $50,000 used. Personally I own Klipsch Heresys bought in 1977 and La Scalas vintage 1978 they would be more in line with your system, but your have to like very clean midrange and treble because they are horns, they will play as loud you want but don't expect deep bass. Check out Klipsch Fortes and Choruses for more deep bass.
Dalquist DQ-10..Although this was introduced in 1973, there was clearly few that competed with them through 1980. Many versions exist through 1982 including mirror image pairs (1976), and crossover changes (1977). The only issue is that they need power. I believe they were 89db/1w/1m, but don't hold me to that. They would do well with about 150 watts/channel. Is your reciever high power?
Beveridge 2SW-1 Electrostatics were reviewed by many publications and were considered by some to be the "best in the world". As a very low production, hand built product, they were not sold in large numbers, but they were a fascinating design, and as it turns out, quite reliable. Mine are still making beautiful music, and they were built in 1978.
mission 770 - have a pair still making music up at my cottage useing a phase linear 300 amp and SAE mk2 pre amp and the very first sony discman as source
klipsch cornwalls were pretty darn cool too. Traded my Heresys for a pair...wish i still had em.
No question the Dahlquist DQ-10's if you want a refined "audiophile" sound. They use the Advent woofer, which was the best thing about Advents, they're time aligned, and they have hands down the best midrange of any speaker from that era. And you can make them much better than they were very simply by replacing the horrendous Motorola tweeter with something newer and smoother, and updating the caps which are easily accessible from the rear.
Plus - they look much cooler than any of the alternatives.
My own fav's were Quad and Spendor BC1; for what they did well (midrange) people put up with what they didn't (deep bass, loud volume).
I also liked DCM Time Window. Vandersteen 2 was probably around and should be viewed as a contender.
However, my musical tastes are different and you might be happier with JBL's and Klipsh's. This is not a put down, just memory of what rock loving friends liked.
Polk Monitor 10B's. I had mine for over 20 years. They're still being used by a friend of mine whom I sold them to. Not bad at all.
AR-9 by Teledyne, inefficient powr hungry beasts but still are good speakers even by todays standards.
My vote would be the Snell Type A