I've used the SSL 2+ as part of my day job in the MI/Pro Audio world.
The 4k button on the front panel is not like the audio equivalent of 4k resolution in the video world or anything like that. It's their term for coloring taken from their legacy analog boards. I tend to like it engaged, but it's not a resolution-related thing. It's more of analog-flavoring shortcut.
(yes, the 4K label is derived from the 4000 series)
At the price, it's damn hard to beat the small-format desktop SSL interfaces, but that's a discussion for another day. I'm a fan. I also like the "Six" mixer they came out with, but that's a little bit more skewed towards other applications like live and such (yes, you can use it in a recording rig, too)...