That' a low bar to hit. I went with the 7900X which is 12/24 coming from a 12700K 8/20.
The game side though is dependent mostly on your GPU though. I ended up picking up an A380 6GB GPU for the Plex processing I do as it cuts the time significantly using QSV which is an Intel thing. The A380 cut times to 1/8th and CPU load considerably to be very worthwhile.
The nice thing is you have a GPU already which will keep the costs down a bit. From the ground up my setup came to ~$900 but those prices are out of date even as about a month later the CPU dropped by $100+ and I'm sure the other stuff did as well.
However, there's a new AMD G series out that packs a punch for iGPU that's priced pretty well.
https://pcpartpicker.com/products/compare/bwxRsY,3hyH99,K4vD4D/ - these would be my choices
For the MOBO there's a few options but, it's more dependent on what kind of other features you might want.
I went with ASRock because they're a good value for the performance and less likely to gimp the slots when you add more cards to the mix.
https://pcpartpicker.com/products/motherboard/#sort=price&m=7&c=159
The PG Lightning is the one I grabbed for $160 on Amazon
https://pcpartpicker.com/list/jpYPHG - MOBO/CPU/RAM/cooler ~
$667 but, if you hunt them down individually you can probably slash more off that. The CPU though is new so not much wiggle room there. There's some new CPUs launching though in the next couple of months but, can you wait it out or need something now? Always the quandary and the inconvenience of a dying setup always puts the pressure on making a decision on unplanned things.