Evaluate my Subwoofer Choice Please

I have been looking for a moderately priced subwoofer to go with my KEF iQ5s, iQ1s, and iQ2 home theatre system. My room is 17 ft by 10 ft and used mostly for TV and movies, not much for music. It doesn’t have to be a KEF subwoofer but I just discovered they are on sale half price. Regular $640 U.S. for $320 U.S. for the KEF PSW2500. I reproduce below a paragraph of description for those not familiar with this model.

As the lower frequencies play such an integral part in recreating the 3-D soundscape encoded in digital formats, your choice of subwoofer is critical -- especially if you want to enjoy the level of sonic immersion you experience in a modern cinema. And really, who doesn't? With a high efficiency 250W on-board amplifier driving a 10" down-firing woofer, the KEF PSW2500 has the power to deliver heavyweight bass effects without sacrificing clarity, and, perhaps more importantly, without lurking in the corner of your living room like a mini-fridge with intent to kill. 33 – 150 Hz. With ground lift switching and movie/music modes, output is easily adjustable to match the main speakers and room acoustics. The attractively-styled, elliptical-section cabinet is massively internally braced to eliminate unwanted internal resonance, and finished in gloss black, matte black, dark apple, maple, and silver to complement the rest of your KEF iQ Series system.

So, my question is, does this sound like a good deal for $320 or are there better subs in that price range? And sorry, I don’t want to spend more.
A couple of related questions: Is “down firing” a good thing, and do I need a subwoofer cable or will any RCA connector do?

Re: Evaluate my Subwoofer Choice Please

SVS in Canada for just the PB10 works out to $639 Canadian with the shipping (plus tax on top of that).
That works out to $511 U.S. Too much over my $320 U.S. budget.

Re: Evaluate my Subwoofer Choice Please

I just picked up the KEF PSW2500 ten inch subwoofer. They had it hooked up to a system with other KEFs and it sound decent enough to my ears. A Soundstage 12 inch and a JBL 10 inch in the same price range were options too, but did not blow me away.
If the KEF subwoofer was not on sale (reg. $800 Canadian or $640 U.S.) I would not have bought it as there are better $800 subs out there; plus $800 was out of my price range. For the $400 I spent ($320 U.S.) I feel I should be happy. The store is good too, as they have a decent "try it and return" policy so I can give a few good days of testing.