The bad thing about that unit is the limited external connectivity. If you look at pictures of the BACK of the unit, you see very few ports to connect other inputs. There is one digital optical input. You could connect a TV or a media player but not both.
I am guessing you are asking about used equipment, since it looks like that is an obsolete model. If it is cheap and better than what you have, you might be OK. But you will be very limited in connectivity.
It is used, yeah. I already own a logitech z506, which i want to replace with this one. I have a tv with a coaxial output, so conectivity is not much of a big deal for me. Would it be much of a difference in terms of sound?
edit: i dont get it. both are labeled as 70/75W speakers but the sony is much bigger...do they sound the same?