Hi Dana , be sure to get mat display , and beware , extra resolution means you have to get bigger size to get confortable ....
think maybe lower resolution but two screens ... i have 4 k resolution on my dell laptop and even close its a no go , i down scal ( you can feel the lost of crispness in my youtube video now versus when don on my elite book hd)

With the screenstes and x ray i really don t feel the need for two screen or extra resolution , may be a small screen for metering suites ...( you can even use your ipad like i do with an app called Duet)

Take your time

Hi Dana , be sure to get mat display , and beware , extra resolution means you have to get bigger size to get confortable ....
think maybe lower resolution but two screens ... i have 4 k resolution on my dell laptop and even close its a no go , i down scal ( you can feel the lost of crispness in my youtube video now versus when don on my elite book hd)

With the screenstes and x ray i really don t feel the need for two screen or extra resolution , may be a small screen for metering suites ...( you can even use your ipad like i do with an app called Duet)

Take your time

Just to chime in here, I recently installed a 40-inch Samsung 4K screen (60Hz, 4:4:4 chroma subsampling) on my Sonar machine (2010 Mac Pro, Win7 Pro x64) to replace my 30-inch Apple Cinema screen.  Overall I'd say it was a baby step forward.  Here's why:
 
My working distance is 45-inches away due to the placement of my M32 mixer between me and the screen.  I was running the 30-inch (2560x1600) at 125% XP-scaling in Win7.  For my 60+ year-old eyes, it was right on the edge of tolerable for reading track names and the control bar.  
 
When I installed the 40-inch Samsung (3840x2160) I tried the 'Vista' style of scaling, and a mere 110% in Win7 was nicely visible but the horizontal 'gain' control in the track view would not work correctly.   Went back to the 125% XP-scaling and everything was about the same marginal discomfort level as the 30-inch.  As I type this, I'm using the re-purposed 30-inch Cinema at 125% on a Win10 machine at 32-inches viewing distance and my eyes are relaxed and happy.  
 
I may re-visit the unsupported use of Win10 in the 2010 Mac Pro and play with its superior video scaling.  I'm going slowly back into Win10 on Mac Pro because it was on an SSD that hadn't been booted since December 2016.  When I tried it two weeks ago, the Anniversary Edition update behaved like a raging bull with a hand grenade.  It destroyed my Yosemite partition, and broke all the permissions on my primary *and* backup data drives so that Win7 saw nothing at all when it was afterward booted.  I spent 72 solid computing hours restoring everything back, so as you may imagine, the "once burned, twice shy" rule applies here.  
 
Pertinent to your decision, the working distance is a critical decision.  If your eyes are at a distance approximately equal to the diagonal screen dimension, then i think you're going to find that 4k UHD is a challenge to read text at 100% (no upward scaling).  Closer than that, you'll have the "front-row-at-the-movies" needing to move your head to see all the screen real estate.
 

Hi Gary! Sounds frustrating! Personally I don't mind head scrolling as I do this already with multiple monitors and jumping to 55 inch yields significantly larger fonts at 4k with no scaling. Surprised no one's gone there on the forum! Will have to seriously think this thru as my new home  actually has a huge room (currently filled with family overflow) which might even handily 65 in, yielding even bigger fonts and allowing further placemet from the wall mount which will be better, spearker placement anyways!
 
I'll  report back once I've got video production sorted, which may entail finally adding my first Apple products to my life! Just love final cut X's  modern editing tools like the magnetic timeline and it handles my new GH5's 4k/60fps output. All of these will be the next big upgrade package and need to work together! May even learn LogicPro just to get my hands on the new Alchemy!

For what it's worth, My experience with my iiyama 40" 4K monitor (not tv), in front of which I work at least 10 h a day.

GaryMedia
Just to chime in here, I recently installed a 40-inch Samsung 4K screen (60Hz, 4:4:4 chroma subsampling) ...

 
Amid all of the great info Gary gave on scaling, size, and distance, I didn't want this little spec to go by unnoticed. Regardless of resolution, ensuring 4:4:4 chroma subsampling will save you from lots of trial/error when hooking up a TV as a PC monitor. Anything lower and text will be ghosted, which for me is a no-go from the starting gate.

Thanks, los great info, especially as I'll be doing video work and chroma key

@Vastman you bet. For those of you who want to be sure, you can take the torture image posted in this blog and if if every line is clear, then you're good to go.
 
Like the videos say, chroma subsampling (anything lower than N:N:N) is an easy way for manufacturers to cheap out on the display chipsets, because compressed video (like MP4 and QAM TV) is imperceptibly degraded by it.
 
On Edit, NB: While you're torturing the display, you may also want to check all supported resolutions and frequency settings. At the current stage of the game, some TVs could kick in subsampling of 4K at the higher refresh rates, so watch out!

Very interesting discussion. Cant wait to hear what Vastman ultimately chooses. I dont have a 4k monitor but my understanding is that a 60in 4k would be essentially equivalent to 4 1920x1080 monitors. If I opened Sonar in this environment (no scaling) wouldnt it just fill 25% of the screen real estate. I get that being able to drag various views to other parts of the screen would allow for more on screen info (on a lesser scale I do that now with 2 HD monitors). What I do not get is the assertion that fonts (i take that to mean individual characters, not actually font sizes) would be bigger. It seems that, without scaling, one would need to sit at comfortable viewing distance for a 30 in HD screen. That results in the "front row" problem when the screen is 60 in.. On an HD monitor, if you zoom the scale, the characters obviously get bigger but some of the image will disappear off the screen edge and you'll get drag bars. The 4k will allow you to zoom without going "off screen" and without drag bars. Thats a big advantage - but only if scaling works well.
Brian