there's no skinny tv with good sound just because you can't get decent speakers in there. Make a really big difference.
This is the fundamental problem, modern TVs are designed to be thin and light - because that's what most consumers want - but this means that there is limited ability to fit speakers. In the good old days where a 32" CRT TV sat in a massive box, sound quality was excellent as there was sufficient space, but this is no longer the case. Older plasma and LCD TVs were also much larger and whilst there was a step-down in audio quality there it was not as big as to modern TVs.
I have a Sony TV and despite being a relatively premium product, the sound quality is very laptop-esque and whilst I could survive with it I chose to add a sound bar as we often listen to music rather than watch TV and it makes it a lot better.
If you just watch broadcast TV you'll probably be fine, it's a lot of dialogue and although the music will sound like it's coming from a laptop speaker, it's bearable. If you ever watch a feature film, you'll regret not getting a better audio system.
As for hiding cables, it really depends how and where you plan to fit the TV, presumably you will have (at least) a power cable running to the TV, so you have some cables being routed around there. We've got our TV mounted to the chimney breast and have a bracket which holds the soundbar below the TV. You can see the cables (both power and HDMI) running to the unit, but they're relatively hidden and certainly I don't notice them particularly in use, and whilst I could have spent longer arranging them, I had other things to do at the time so never got round to it.
If you do opt for a sound bar, I'd suggest getting one with a wireless woofer unit, this means the soundbar itself can be smaller and therefore less obnoxious. We've got one from Denon and was good value for money when I got it a couple of years ago as it was on offer at Currys in the January sales and I got it for less than half it's current (but still discounted) retail price, so if you do wait you can get a really good deal.