single speaker unit....misnomer
Calling something like the Yamaha a "single speaker unit" is quite off the mark.
As it contains 16 precisely placed and angled speakers, a microphone (for setup) and some clever electronics it can easily ask for 700 quid, because it sounds as good as other 700 quid systems after they've had some serious setup-love. The funny thing is, the Yamaha only needs a single button push for all that complicated setup.
Of course if you think that surround means buying a Logitech 7.1 system and plonking the speakers wherever is convenient then you've kind of missed what surround (or even stereo) is about. For spatial accuracy the speakers must be placed correctly, with room acoustics and all that crap taken into account. Setting up a simple pair of stereo speakers can easily involve playing around with location for a few days. And I'm NOT an audiophile, this is just to get a good and precise stereo image out of decent-ish speakers used for mixing music (nearfield monitors). Even cheap plasticky speakers can be improved by good placement, but in the end they'll always be crap.
180 quid is where decent speakers start, and toys stop. Unless you just want sound to emerge from an old transistor radio with a single crackly speaker, which is a perfectly valid approach. But if movie surround is the issue, then it's hard to beat the Yamaha soundbar without a lot of effort.
(I used to sell this stuff, older models, and was always blown away by the quality/ease of operation.)