4K is not really about "what looks good on a 60" screen" -- it is more about the color depth. The benefits of this are really challenging for most folks to even think about because our "real world" of crayons, chalk, paints, make-up, and clothing is based on "analog color" where the difference between one color and another is achieved with infinitely tiny tweaks or physical pigment. In the digital world the bits that are available to record and reproduce color are totally discrete and when we increase the bit depth we allow more accurate gradations. Here is a little demonstration of this works -- tricky to illustrate what the limitations are -- http://www.cambridgeincolour.com/tutorials/bit-depth.htm
I also would point out that 4K resolution is very obvious with a high quality projector. The most value priced 4K projectors are still well over $5000 but honestly I have seen even regular DVDs and broadcast content upscaled on the Sony projectors and the image truly is a "night & day" increase in the visual impact. The pixels are so much more tightly packed and smoothly animated that everything seems far more lifelike. The technical details of what happens with modern upscalers are kind of amazing -- http://www.cockam.com/viddoubl.htm
The same sort of "wow this is MUCH better" is also true regarding Atmos (or DTS-X & other immersive / object oriented formats). As the sound designers have gotten better at working with the whole production chain, from writers and directors to effects people and even actors) they have learned how to really create a far more convincing "acoustic space" in their movies. Just like I can take a blindfolded person and have them instantly tell me "I am in an office / now I am in a hotel room / now I am in kitchen of midsized home" as the same dialog or ambient sounds are repeated -- it is possible to really make the whole sense of being in different kinds of "space" driven by immersive audio technology. Folks that are old enough might recall the not very convincing efforts to use digital reverb to simulate a "concert hall" vs "jazz club" and the reason for those failures actually trace back to the differences that a once very innovative Dr. Amar Bose worked out regarding direct vs reflected sound. It is not just time delay! There are actually different properties of which frequencies get reflected / absorbed. Hard to do that without tailoring the speaker outputs!
Unfortunately until recently the amount of calculations and data needed to get ALL the timings, frequency curves and angles ACCURATELY plugged in made such efforts "muddy" but the innovations in DSP chips have made it possible to keep the DISCRETE info in the dedicated channels and seamlessly reproduce a huge range of startlingly convincing environments. The well done home theater installations in homes or dedicated showrooms cannot be compared to the "quick and dirty" simulations that chain stores attempt...