Honestly its really hard to compare and contrast, and a lot easier to just say I am very pleased with my TV and gaming area and equipment.
I was using digital optical from HDTV to receiver, mainly to get TV speaker audio and also have smart TV features and PS systems swappable with the TV remote instead of changing received inputs, but after finally getting more HDMI 1.4 cables and "unlocking" Dolby DTS HD, I can't say I'd go back to any impure methods.
As a few reference points, Interstellar ended up being played about five times in three days. Also yesterday morning I was playing Driveclub, which occasionally has some thunder rolls and pretty intense weather effects with DLC, real thunder rolled outside and I didn't think it sounded realistic enough.
As you get better speakers, either on entry or with upgrades, I'm sure the differences may become apparent, too.
I think for me, its mostly about confidence "everything is correct."
And also don't worry much about 4k BD, but I also think, unlike 3D, 4k is catchy enough to stick, so I'm sure also production companies will eventually try to sell 4k BD, but I really think upscale will be just as great.
Replacing all your stuff would likely be a losing battle, though.
Also, a link pretty much discrediting everything I said soooo, whatever, but I still believe what I said (until my eyes prove me wrong): regular 1080p with TV doing 4k upscale and HDMI supporting Dolby DTS HD should really be kicking all the butt you need.
I guess it's important to have surround receiver that supports 4k pass through, I'm unsure if a 4k bd player or just ps4 firmware update is required for actually support a "UHD BD.
http://www.extremetech.com/computing/205593-ultra-hd-blu-ray-standard-finalized-4k-support-hdr-digital-bridge-sharing
Sorry to BS so much saying "not to worry," but I'm not worried and I worry about most everything that goes on a shelf or into a computer.