I couldn't find it on the site. Maybe the english version is smaller.
My guess: 750 Watts is only its peak output; this means microsecond bursts and
not continuous power. I think it's a deceptive act to use this value as a sound system's listed attribute.
Here's a link to a fairly good 760 Watt amplifier. It's stereo and is probably about average for the size of a decent high-powered amplifier: it weighs almost 40 kilos and is a half meter wide and deep.
If this is the set you're talking about:
and I saw it listed for 30 euros, then you could do worse. However, the specs I read on it can't be true. The site I saw it on (had to do a search since I couldn't find it on USBlaster.com) listed the "sub" woofer as 20Hz - 150Hz. I can't imagine it going to 20 Hz, not by a long-shot!
More suspicious specs, and only suspicious specs!
If those are flat panel speakers: cheap flat panels almost always produce sound far inferior to traditional cone drivers. Monsoon flat panel speakers are probably the only adequate made-for-pc flat panel speakers that have been comercially sold.
At least it's pretty and cheap, but I expect that it's basically crap.
sorry to be such a downer..