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 at Visions. Regular $800 for $400 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 $400 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?

I HAD a down firing, 10", 250w, SW250 Sub that was about equal to what you describe. It was the one recommended with my with my Wharfedale surround set.
I was not happy with it at all. To get it loud enough i'd turn it up, but then it would max out and distort. Plus it didn't go anywhere near low enough. I sold it for 400 (I paid 800 plus tax).
I built myself a set of 15's. You don't have to get that extreme. Read all the previous posts about what sub to buy. PB12-Plus seems to be highly recommended. I'd call that a minimum requirement.
The new PB13-Ultra gets really good reviews but way beyond your price range

... does this sound like a good deal for $400 or are there better subs in that price range?It sounds like a very average deal for $400. The Klipsch Sub-12 (http://www.klipsch.com/products/details/synergy-sub-12.aspx), currently on sale at BB for $420, is probably a better buy:
- 12" driver (down-firing, rear ported)
- 300W RMS / 650W dynamic BASH amplifier
- 24-120Hz +/-3dB

A couple of related questions: Is “down firing” a good thing, and do I need a subwoofer cable or will any RCA connector do?There's no real disadvantage to down-firing (versus, say, front-firing). A good-quality RCA connector will do just fine.

I just picked up the KEF PSW2500 ten inch subwoofer from Visions. 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 (1/2 price) I would not have bought it as there are better subs out there in that higher price range; plus the regular price was out of my price range. For the money I spent I feel I should be happy. Visions is good too, as they have a decent "try it and return" policy so I can give a few good days of testing.

If you have the opportunity to do so, demo the Klipsch Sub-12. I think you may find it to be worth the $20 premium over the Kef.

If you don't have the opportunity to do so, enjoy your new sub. :)

It sounds like a very average deal for $400. The Klipsch Sub-12 (http://www.klipsch.com/products/details/synergy-sub-12.aspx), currently on sale at BB for $420, is probably a better buy:
- 12" driver (down-firing, rear ported)
- 300W RMS / 650W dynamic BASH amplifier
- 24-120Hz +/-3dB

There's no real disadvantage to down-firing (versus, say, front-firing). A good-quality RCA connector will do just fine.
I was allways under the impression that Front firing Subs were better in basements with cement floors. I was told that down firing subs lose too much bass through the cement. Does anyone else have any opinions or facts about this theory? I'm all ears.

I was told that down firing subs lose too much bass through the cement. I use a PSW110 (set half way for power) down firing port on concrete floor (carpetted) and do not have any bass management problem what so ever!

Floor Coupled Port*
All woofers feature a floor coupled downward firing port. This configuration brings you maximum bass impact while keeping the front of the cabinet as low profile as possible.

punman, I think you made a good choice for your system... The most important is demo which you did and seem to be happy with!

Cheers!
René