Sony HT-DDW685....5.2 channels

I don't know anything about that particular system, but don't worry about it being 5.2 channel.

Essentially all that means is you're adding another subwoofer. This is no problem, and actually a lot of people with home theater setups run two (or more) subs anyway. This increases bass impact as well as the "eveness" of the bass. It is just a clone of the LFE channel though and not discrete.

If you look at the back of that system, there's not a lot of connectivity options. Its pretty low end. Its essentially the same as the HT-DDW790 here. Inexpensive but a decent starter set I guess.

Is the original poster abroad? I think there are better options if you're in the states.