Normally integrated sound pales on any HDTV in comparison to nearly any off the shelf surround/stereo system from a big box store, etc. You can't properly place the fixed speakers where they truly need to be with an HDTV, so you lose out on good sound.
That said, I *do* feel Sony has some of the better built in sound of many of the HDTVs, especially the smaller ones. Haven't heard many of the larger ones since at that price point, most folks are mating them up with decent sound systems and could care less about what the built in speakers sound like. YMMV.
If it's intended for a main room I would go for some sort of basic surround system if possible. You won't regret it.
I don't want to use extra speakers. I had a Sony Plasma KDE 50 XS955, which had an excellent sound. I'm now looking for a similar sound in a HDTV.