Yeah the caching thing is totally not necessary, its just one of those lesser-known options you don't hear about often and I just thought it was cool to note that in case you could make use of it
As for GPUs if you absolutely need new you can find RX580s all day for around $180 or sometimes you can find them on sale for a bit less. I'm not sure if they're gonna be around much longer as the 5600/5700 are beginning to take the spot as their new mid-range offering before Big Navi GPUs hit. As for Nvida you can sometimes find 1660 variants for right about $240 and sometimes less depending on how its clocked, but if you're okay with used you can find 1060 6gb models for around the same price as RX580s with a little better performance in some cases. All of those cards listed will work just fine for Med-High 1080p games at a stable framerate.