FWIW, I have the DAV-IS10 and am really pleased with it. Yes, you'll probably get better performance and/or value with a separate amp and speakers but that's missing the point of the DAV-ISxx which is to provide a decent surround sound while being visually very unobtrusive. Our living room is small and expensively (but sparsely) furnished, so boxy speakers were just not an option.ÿ
The performance of the DAV-IS10 will obviously have limitations because the speakers are so tiny, but we were amazed at how good it is - especially now we have the blu-ray player going into it, the (non-HD) sound is great from that.
Few things to be aware of:
1) the speakers are tiny, so the midrange is filled out by a mid driver in the sub, so the sub is somewhat directional (needs to be near the screen)
2) the sub is huge (I guess because it has to do extra work because the speakers are so small), and an odd shape (not a cube, but tall and thin)
3) there aren't too many inputs for other sources, and no HDMI input. We have blu-ray into the digital co-ax 'TV' input (when the blu-ray's off, this reverts to the stereo analog audio from the TV), and Sky+HD into the digital optical 'SAT' input.ÿ
4) if you go with the 50, be aware that the rear speakers are still wired, just separate set of wires than the fronts. we went with the 10 and had no problem concealing the wires - which are long enough to be routed around the room.
5) if your room is large, it might struggle!
6) it's normal to have the volume up to 58+ for normal listening. that's just how it's calibrated, don't ask me why. maybe Sony are big Spinal Tap fans. "but this one goes up to 110!".