I also have the KW500 and it is fantastic. I am running it with Aerial Acoustic Model 6 speakers (wow!)
I do think the MM input can easily be bettered, my Liberty Audio B2B-1 runs rings around it, but it should for it’s price.
I have also had an A308 (full sounding even when turned down) that was great and other brands/models I have had are Audiolab 8000S (years ago!), Krell KAV300 (thin at lower volumes) and a Pathos Logos. Only the Pathos did I like more, but after a finicky operation and a failure (I got it fixed) I got rid of it. The MFs are bombproof, you can’t go wrong.
My best buddy has had MF A1, B200, F series and currently has a Nuvistor Integrated. I’ve listened to them all and think they are all fine sounding and great value, but I think the KW500 is special.