I also built my current rig around 2013 or so. Originally configured, I believe I had an i5-3570k in it, 8gb of DDR3 clocked at 2133, a GTX 760, and a 750-ish watt Raidmax psu. The case is still just some cheapo Apevia X-Hermes. I think it cost $50 at the time. For storage, I started with a 1tb WD black mechanical hard drive. That's bloated various times over the years, now up to a 1tb Samsung Evo 840, a 6tb WD black, and a 2tb WD black. I still use the Corsair K70 I bought not long after (my first modern mechanical, not sure otherwise). I believe my EVGA Torq x10 is only slightly newer than that, and I didn't pay a huge amount for it.
Not long after the release of the 10 series, I upgraded to a GTX 1070. In the last year I picked up a treasure trove of i series and Xeon processors at a recycler for $7 each, having dug them out of a scrap bucket ... including the i7-3770 I upgraded to. I bought two separate 8 gig sticks of ram used on Ebay to bring my system to 16 in the last few months. I have faster processors around, just haven't bothered to switch to another socket just for gaming. It is handling Red Dead Redemption 2 on max just fine, but I do want to build a new Ryzen rig once I bother to ATX mod a XPS 720 chassis for that purpose.
My primary gaming monitor predates even my rig. I have an old Samsung 21" (or so) 1920x1080 display I got back in 2009 or so, on Black Friday, for about $120. I was still using my very first desktop computer when I got that display. Still looks beautiful, so I have had no reason to replace it unless I want to make the jump to 4k. On either side of it, I have a 23" (or so) 1920x1080 Westinghouse led tv I got at Goodwill years ago now for something like $100 (when displays like this were first coming out), and some cheapo 21" (or so) 1920x1080 Acer touch display I got for about $100 new at some point for when I had a monitor wall mounted above my bed with a knockoff compute stick. All 3 are mounted to the desk, the side monitors mounted with gas spring arms that cost me a little bit more than the displays themselves.
My speakers are a set of Bose Companion 2 Series II speakers I picked up at Goodwill years ago for $7.
So, my setup is a random amalgamation of once-premium things and/or random scrap and/or thrift finds. I guess I'm not too picky if it gets the job done just as well as anything else. I don't do much typing on that computer, so the mediocre Cherry MX reds suit me just fine.
I agree on 4:3 being nice. I have very little desk space at work. At the high school, I have two 2003-ish vintage Dell business class monitors in 4:3, mostly for their fancy proprietary stands. Those, right next to each other, already take up a lot of space, and I have just enough clearance left to see when students come to the help desk counter. Honestly, the biggest use I have ever seen for 16:9, even at home, is to tilt the display 90 degrees and use it that way for reading articles and/or going through long vertical lists, but even spreadsheets too. I may eventually go that route at work, I do a lot of copying and pasting, and recording/logging things in Google Sheets.