Without much experience with any of them to offer a sonic review....
1) STA-95 I've always loved the dark metal look and slanted meter display.
2) SA-500 Power meters, nice layout, and that era Technics had some great specs
3) DA-R8 Well it's just so darn cute!
That's pretty much my selection too. I've had all 3 of the above, and still have the STA-95.
I love the Mitsu but the Darlington power packs were problematic. The SA-500 was chopped because I have too much gear and something had to go.
I had that Sherwood 7100a too I think but it had a bad power switch built into the volume control. When that failed it was kaput. The flakey Pioneer would drive me nuts.