You're going to want something with 4k passthrough if you want some future proofing
HDMI 2.0 is getting released soon but as i understand as long as you have 4k passthrough not having hdmi 2.0 isnt a killer
also with new audio formats like "dolby atmos" (based on some yamaha tech) you may be interested in a 9 or 11 speaker capable receiver (but they're expensive) for some future proofing
I've never been a Onkyo fan because they've a history of getting
HOT and breaking down
I've always been a fan of Yamaha always solidly made (jap parts) and excellent mix of features and quality sound
But people seem to lean towards Pioneer because they say it handles bass better (and are also very well made and sounding)
Denon i've never looked into much but have heard people praise them
I would also consider a NAD receiver as they allow upgrading (like your desktop pc) they're excellent excellent receivers but they're barebones not like other receivers that include more features than simply working your speakers
A/V Receivers - NAD Electronics <these will help in future proofing without having to pay a lot initially
check out some review sites there's normally extensive reviews available from sites like
http://www.whathifi.com/ http://www.audioholics.com/ http://www.hometheater.com/
I recently picked up a receiver too btw from a local place
http://www.ayreborn.com/ he usually has sales and when he does his pricing makes it easier for me not to bother to drive over to the states