Reflection

Good day everyone, just dropping in and I was in search of a quality receiver for my Klipsch R-625FA 5.1.2 set up. Primarily I see that this is an expensive hobby or rabbit hole for your average Joe. Just trying to get the most out of my new TV which I had for a couple of months. The only issue I keep on snagging and I do not really understand, and an explanation would be greatly appreciated. First, which receiver to choose and second leaving some room for expansion if possible with budget. I have a really bad budget at this time so everything is appreciated, but direction is everything. Im trying to spend 600-1000 so just keep that in mind, not sure if it's doable. Now my next issue is I do not understand how this works exactly, so my receiver is going to connect to my tower speakers twice? one for the front firing and one for the dolby atmos? Just going by what it looks like on the rear of the 625FA. Because I see these 5 channel receivers and it looks like it only has 5 connections on the rear, doesn't it need to have 7? it says dolby atmos receiver which is making me go Hmmmm...? I will swap out my center for a 404C, as my research shows that the center seems to be crucial part of the set up. So I am going to be putting in additional money on top of this all as this system comes with the 52C. Thank you for your time and your opinion, I really hope I could join the Klipsch family soon!