Unless you're an audiophile, I am going to say that there will be little to no difference. The reason being that the speakers used are the same; just six more in the Harman Kardon. That, plus some additional listening modes (e.g. on stage, or audience), and probably ClariFi (which most of us turn OFF anyway; it causes funny sound distributing issues for some listeners), are the only differences. So, more granular distribution of sound is the main difference. As far as quality of bass, middle and treble, there won't be any difference. I could be mistaken about the amplifier being the same; if the HK comes with a stronger amplifier that could make a difference; but wouldn't that mainly be only when you really crank up the volume? The "factory" stereo is just lacking the extra speakers: but it still gets the two floor-mounted subwoofers, which is the really telling comparison, in my humble opinion: had I known that the HK was not the only system with woofers, I'd have not automatically made the HK surround sound a "must have" on my short list: I'd have listened and compared to see if I had to have the HK or not.