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. 
vasubandu
We also have a Panasonic plasma screen but I have decided not to upgrade for the time being. I had a look at many modern 4K screens and felt that the ones that I saw were pretty gross with too bright colours. But that may be the way they were presented to impress in store. For me the clinching argument is that there is virtually no source material to watch. Broadcast TV here in the Netherlands is not even full HD, and the number of UHD disc is tiny, and even fewer of them are serious art films. I know Netflix does some (compressed) 4K streaming but I have never found anything other than commercial drivel. So on the TV side I am postponing an upgrade. My plasma screen should have at least another few years of life in it (I hope).
On the audio side I have long ago decided that I prefer a high end stereo system for my HT sound (Quad 2805 speakers with a B&W PV1d sub plus Antimode 8033 room eq). For the same budget and the same domestic space I think I get better sound that way, although admittedly I am missing some of the special effects. But that is my choice, and your preferences may be different, of course.
Makes complete sense. We get enough HD content in Seattle to make it worthwhile I hope. My problem is that I am so out of touch with developments that a likely to make a mistake.  Interesting thought for stereo with home theater. My boys love the sound of things flying overheard.
To be precise:
We get what is called HD ready i.e. 1280×720p broadcast/cable television. Full HD as in Bluray discs is 1920×1080p. UHD/4k is 3840x2160 pixels. Do you have significant UHD content, or just HD? If the latter, it is not yet worthwhile to upgrade, I would argue.