Hi, I have recently been thinking about upgrading my current home cinema system. I have narrowed it down to either a new subwoofer or a new surround receiver. My current subwoofer (Paradigm PDR-10) and receiver (Sony STR-DB840 ) have served me well over the last 10 years, but I need some help on deciding which component to upgrade first and some recommendations on which models to audition. My budget as £500. My system is used for Movies, Music and Gaming: Sony KDL-32W5500 Television; Sony STR-DB840 Receiver; Sony PS3 Slim; KEF KHT-2005.3 + Paradigm PDR-10 Subwoofer; QED Performance HDMI; TCI Coral Optical; Chord Carnival Silver Screen. Thanks