I recently got a Sony W8 TV and am now looking into upgrading my surround sound system since the sound is always out of sync and it's looking like the only way to solve it is to hook it up via HDMI which my older system does not support. I currently have a Sony STR-K790 AV receiver speaker bundle and have been happy with the sound quality and bass, so would ideally like another Sony av receiver with at least an equivalent spec. I've been looking at either the Sony STR-DH540 and STR-DH840. The DH540 appears to have a slightly lower power output to my current receiver (750w compared to 800) but the DH840 has quite a steep price increase for the extra power. It also has 7.2 surround sound which I don't need, but does have wi-fi which is appealing. Can anyone vouch on these systems and whether or not the DS840 would deliver superior sound to justify the extra cost? Also my current speak came in a bundle with the speakers, whereas this does not. Should the speakers that came with it still suffice or would they be worth upgrading as well?