I would buy the tv and try it. That's the only way to know if you'll want a sound bar or not. I have 2 large tvs 1 a new led and the other a top of the line plasma. Difference of night and day between the sound systems but of course the plasma with the good sound system was 5 times the cost of the led.

They put cheap sound systems in the new one's to lower price knowing most people will end up buying the soundbar too. It took a while but by messing with the sound control settings I was able to get cheap tv to be good enough not to need a soundbar but still nowhere close to the quality sound system in the expensive tv.