The RF-590 has a sterling reputation, probably in top 5 of all time.
One un-noticed gem is the 505A, which I believe is the best SSB receiver ever.
It had a squelch which only responded to audio (not noise). When I had the 505A
I also had about a dozen other super-RXs, and the 505 picked up weaker signals
more clearly than ANY of them. Since I used a single antenna feeding a
multicoupler, each radio got an identical signal...no question of switching
antennnas, etc.
I'm sorry I ever sold it.
Two issues: it is not a tune-around receiver (set it and forget it), and you
MUST use the preselector tuning control; intermod on the AM band is not
acceptable.

The ISB capability (simultaneous USB and LSB) is cute. Two programs on VOA
feeder circuits, and on occasion, 11175 had USB and LSB activity at the same
time.