I got a Rex 3 about a month ago and love it. Was running Pass Labs XA 25 and X 250.8 before that. While my Pass Amps are great, I prefer the Rex. Instruments and voices are more solid / fleshed out than with the Pass Labs. I've been into audio for over 40 years and my wife says the system has never sounded better.
I never heard the VK series but the Rex 3 is a very special Amp.
It does produce a lot of Heat so probably not ideal for small rooms in hot climates.