I have most of the listed units, but many are in various states of disrepair, so I'm not confident voting definitively. In addition, I have owned and used multiples of most of the receivers, and they are all a bit different, though largely similar.
I haven't spent enough time with my restored X1000 to comment - it sounds very good in passing - lots of power as you can imagine, but I haven't sat down with it and played a variety of records. My 5 year old has stereo privileges, so I haven't rotated it into his grubby handed realm.
I'm very impressed by the X100 3 I recently finished, but it has TA600 OPTs, so is not perfectly representative. It's now my 5 year olds bedroom system with some EPI M50's and a Pioneer PL115D. Great sounding little system - at least with his three favorite records by Porter Wagoner, Freddie and the Dreamers and Kraftwerk.
Both my restored 500C's (one super early 13###, one super late 81###) sound similarly great, but then they both have done time with the same Michell turntable and Frazier Concerto speakers. I have had 400's, 500B's, 800C's, etc in same system and they all perform similarly as expected. I am suspicious that just about anything I plug in to the Fraziers will sound really good.
I did a bunch of work to an 800B in terrible condition that I gave away after using for a while. Maybe my favorite I have listened to so far -very present and musical with a great sound-stage. It got extensive work done and had a really nice set of tubes. I have thought about trying to get it back.
My X202B is very confident sounding, it's in a similar situation to the X1000 - I like it better than my KX200 but the KX was pretty rough when I got it, and probably needs additional work and final adjustment.
I have yet to attend to either of my TA800's, TA600 or 500S. I have some tuners to work through before I get on to these.
I like my KX100, but it is mostly original and as such is a little sloppy.
Re; Solidstate units
I spent some time with a 500T, I had low expectations based on the usual Fisher SS bashing that goes on, but I found it to be really good. Very present and powerful, strangely not unlike the X202B. I don't remember if I was using the same Paradigm bookshelf speakers, may have been.
I have spent a lot of time with a TX100 and it's decent despite needing some work (very slight hum, noisy volume pot) - it is used exclusively with a turntable at my house in the mountains and has been paired with some AR4x's and Heresys, both of which it drove without issue. I just got a Technics Quad receiver that will replace it so I can use 4 speakers in the very big main room.