Front/centre & rears sorted so now on the look for some more bass for my movies.

Current set-up in a room approx 4.75m x 4.5m:

Yamaha RX-V679 amp
Q Acoustics floorstanders/centre & rear speakers.

Like to look/specs of the new QA B12 but £500 might be a stretch.

Any recommendations for around £350? Space not really an issue..

Still running original KEF Eggs via an old Yamaha AX620. The KEF subwoofer died a few years ago and was replaced by a BK XLS 200 Mk11 275W FF Subwoofer that is significantly better and within your budget. I use it in a 24′ x 12′ living / dining room and it copes very well indeed. Can’t recommend highly enough.
Linky

i’ve the q acoustic sub (21oo maybe….will have to google)..
I’ve just got a 2.1 set up with Q acoustic BT3s…. works really well with a bit of Billy Bass…

DrP

As per downshep, I’d go for whatever BK with your budget. Great bits of kit, really good for the money, well made, choice of finishes to suit sir’s decor.

I have a Q-Acoustics 2000 5.1 system, and after the 2nd sub failed went with a BK Electronics P12-300SB. Night and day difference.

BK monolith here, big, heavy and awesome. They have b-grades on their eBay outlet; I’ve been waiting for a eBay 10% code to buy a something slightly smaller for the kitchen.

What’s their eBay shop called, Junky?
Just been having a look at BK and look good.

Used Rel. Mine is huge and was pretty cheap. Integrates perfectly.

Thanks for heads-up on BK (similar position to OP). I’ve got QA BT3 bookshelf speakers, but it only has a single Subwoofer out port – is that still ok for the BK units?

The manual for there Gemini sub suggests so.

http://www.bkelec.com/HiFi/Sub_Woofers/gemini_manual.pdf

I’m running a single cable to the XLS 200, works perfectly.

Perfect, thanks!

BK subs on ebay:

https://www.ebay.co.uk/usr/colosussxb

Unlikely to find better than BK at that price range.
Single connection is pretty standard as well.

I bought a kit from Winslow audio, very happy with quality and satisfying!

*Wilmslow