Help a guy out? Renovating home theater system after 10 years and have a few questions.

I am going to modernize my family's TV situation.  We have a 60 inch Pioneer 1080p plasma. My speakers are Paradigm Millennia with two MIllenia 20 Trio as towers and then Millenia 30s for center and surrounds.  The subwoofer is a Paradigm, but not sure what model.  The Receiver is a Denin AVR 2807. I have not done anything with it in a decade. 

I am getting an LG 86SJ9570 because why not.  The receiver definitely need to go, and I have settled on the Yamaha Aventage for no good reason. I was looking at Onkyo, but I get the sense the Yamaha may be easier for me to figure out.  My inclination is to look for more receiver than I need but buy something maybe a few years old. Whatever it is will be a learning process.

I have figured out that the model numbers reflect the series or the date.  When the Aventage came out in 2010, it was 60, 700, 800, 1000, etc.  Then they have the 810, the 820 and so on.  So we now have the 70 series.  I suspect that if I bought a 7 year old receiver, I would be missing some things that I really want or need, but I have no idea how far back I can go safely.  I cannot find a chart of the changes by series.  An RX-A1070 is $1,199 at Amazon, and an RX-A2060 is $929.  I can get a 1040 for $550 and a 1030 for $450. But I have no idea what a good cutoff point would be.  If anyone has an idea, I would really appreciate the help.

I also would be curious if my speakers make sense.  We sit about 18 feet from the TV, and I sometimes feel like there is not enough mass to the noise if that makes sense. For some reason, it seems to me like that might be more of an issue with a bigger screen.

Thanks, I really appreciate any help.