If you feel it’d be easiest to get something all together, Onkyo tends to package proper speakers and subwoofers with their various receiver / surround speaker offerings, as they usually consist of models they also sell separately.

Whatever receiver brand you decide works best for you, though (I’ve had some issues with Onkyo receivers here and there, and all Yamahas annoy me by choosing to not indicate the decoding method on its display), you’ll need decent speakers and I HAVE had good luck at reasonable prices with Onkyo surround speakers / subwoofer offerings. You can free yourself up to shop around on the receiver, if you grab some affordable speakers like this: http://www.amazon.co.uk/ONKYO-SKS-HT528B-5-1-Speaker-Package/dp/B002LVU95W/ref=sr_1_1?s=electronics&ie=UTF8&qid=1455649941&sr=1-1&keywords=onkyo+speakers