Not sure on updates on the 2kw; all the sets I have seen were identical as far as I could tell (sonically and visually - except for the prototype pair I heard years ago, of course).
And yes, I've heard them versus 1.2kw - hence why I say they sound more like that - they are from the same generation of design/voicing. The 601 is not. If you think the 1.2kw is an iron fist in a velvet glove, think of the 2kw of an iron size 22 foot in suede boots. The level of control those amps have on... well... anything, is astounding. They still remain one of my all-time favorite amps (2kw) regardless of price. They present in the traditional McFashion: a little top roll-off for a very pleasing, engaging, emotional presentation while still remaining articulate and defined (unlike the 601's which are top and bottom heavy and not in an eloquent way).
The original 2kw's had superb (and countless) binding posts since they expected you to tri-wire (and then some, the back of the XRT2K has 9 sets of binding posts for a tri/tri wire setup). They match the ones of the 402/1.2kw, which is the best binding posts Mc has ever had (far better than the 452 debacle).