Re: speakers should be seen AND heard
The problem is with a full surround sound system is not cost. As you note, you can get quite a decent one for about £400.
One of the problems is space. Do you, or your other half really want speakers all around the room, together with the relevant cabling (even wireless speakers need power)?
Another problem is, as I mention above, cabling. Do you want to have to bury your cable in the walls, or floor, or tack it to the walls? Do you want it trailing across the floor, or hidden behind furniture? If you have it trailling across the floor, it's a trip hazard. If you bury in in the floor, walls or behind furniture, or secure it to the walls, it still takes time and effort.
With a sound bar, you need one mains cable, one cable from the TV/STB and one for the subwoofer (which can be anywhere in the room as human hearing cannot accurately pinpoint the direction of bass sounds). Then there is also ease of use. With a surround sound system, you have to turn on the system and set it to the correct mode and turn on the TV and any STBs..
With a soundbar (or with mine, anyway), you turn the TV and the STB. The sound bar comes on when it detects an audio signal, and switches off about half an hour after the signal finishes.
You are paying (IMO) for a fairly decent sound system, but you are also paying for convenience. When I got my sound bar home, it was properly installed and working 5 minutes after I got it out of the box. I can also pretty much forget about it day to day. It does not sound as good as a surround sound system, but I don't need it to. I just need something that sounds better than TV speakers and works.