Denon AVR-486 HTIB upgrade options
I'm not sure how old my system is - probably circa 2007. I'm using the 7.1 system as 5.1 and my Vizio tv does the input switching (no HDMI on the Denon). I'm debating an upgrade but my current system isn't offensive to me so I don't know if it is worth spending money on. I've got the setup in my basement rec room that is approximately 20'x20' and use mainly for streaming content and movies with a little streaming audio mixed in (70%, 25%, 5%). I wouldn't mind a little bigger sound and easy of use going between the inputs.
I've only got 4 HDMI inputs (Blu-Ray, Roku, chromecast & Xbox one) and TV content is an OTA antenna.
I've looked at some of the new HTIB like the Onkyo HT-S580 and the Yamaha Yht-4950U (Both sub $500 systems) but don't know if I would see/hear any substantial difference. I've also considered just upgrading speakers to the Klipsch 5.1 reference (also sub $500) or just my receiver (I haven't done much research here).
Can anyone help me with some direction? I'd like to keep things under $600 if I upgrade and get a better understanding of what component(s) are the most important if I consider an upgrade.
Thank for any advice you can give.