To be fair bemaniac, the Q700's are quite different to the Q500's. The larger bass and UniQ drivers produce a warmer, smoother sound than the Q500, which I find are ideal for smaller rooms or those that don't want too much bass.
mvg27 - I can't comment on the Polks, but I can give first hand experience of the KEF's.
As far as movies are concerned, hi-fi speaker's have improved drastically over the last year or so, and the KEF's are no exception to that. Their UniQ driver has always suited movies as they tend to be able to place effects more accurately than conventional speakers, and they have wider dispersion characteristics than many conventional speakers too - more like a dedicated AV speaker.
Their wide dispersion characteristics also allow music to be enjoyed from areas other than the 'sweet spot'. Their light aluminium drivers allow quick response, digging up subtle nuances that some other speakers can only hint at. They seem to have an effortless knack of producing a three dimensional soundstage, something many other sub £1k speakers fail to achieve. The can also project sound into the room, which is even rarer than the previous point!
Because of the capabilities of the Q700, it really does depend on the accompanying amplification as to what you get out of them. They're relatively easy to drive, but they still like to be provided with decent current. Something like the Marantz 6003/6004 ornRotel RA04 amplifiers are a good place to start, and the likes of the Rega Brio R and Audiolab 8200A will get more out of them.
Which amplifier are you intending to use with your speaker choice?