The speaker wire needs to be equal lengths for both sides, regardless of whether it "needs" it, especially if it's a low powered system. Just don't bundle up the extra run into a tight coil or you'll cause other new issues!

The next most likely issue is just room acoustics- it's probably just something absorbing too much of one channel's sound. Also, if they are spread way out you're going to get very limited soundtage ability- bringing them in would be better, although I'm sure it's an issue of convenience and furniture placement.

Get equal wire runs first and then adjust the balance knob? Good luck!

I agree w/ Doug. Having unequal speaker cable lengths will worsen the problem. I'm sure you tried a lot of positioning, but maybe you can try a bit more? Near the bottom of the "As We See It" article by Jason Victor Serinus, there's a short paragraph about his experience with speaker placement, the effect that it had...

http://www.stereophile.com/asweseeit/508awsi/

I suspect the problem is pretty basic, namely that 10m is a lot of wire for a compact system's tiny amp to drive, so the distant speaker is going to be putting out a very much diminished signal. Second, I've never heard a system create much in the way of soundstage using small speakers placed 10m from one another. Also, based on five-year-old experience I garnered reviewing compact music systems for Amazon.com, some (not all) are voiced to be listened to in the near field at a desk, so that, while making "sense" from an audiophile point of view, separating the speakers and mounting them on stands might make the system sound worse.