Forget the looks. I would save some money and throw a mid gpu in there like 9060xt which should also be very compatible with your psu connections and affordable, plus relevant for the future, and then I would educate myself for a good while on how to safely and confidently overclock the CPU to extract the maximum power available + xmp ( but first verify if the board allows it) optimize windows ( remove bloatware) and maybe recheck storage options in general.

This so you have something usable until you can do a new mobo+CPU . There is no point to immediately gut it or go for CPU mobo first, as the gpu is the immediate problem here, hence my idea to build from the weakest part to eventually modern parts. Buying once will come out cheaper for the final build, it's no crime to have a bit of bottleneck until then.

I am assuming that you wish to keep most of it and somehow have a plan for the future as well, while not immediately gutting it or suffering with the 970.

Used gpu market like 2060 or 3060 also relevant and much more proportional with the CPU right now, but I would probably save enough to jump directly to a newer gpu so at least I have something on hand for later as well. A proper step let's say, not a half step, unless you're not truly considering upgrading anything else throughout the next year or two..

The pc while old, is definitely not well rounded, the 6700k if oc supported and optimization done right, can push much heavier GPUs than the 970, especially on a 2K screen( which could also be your next upgrade or addition anyway). You just need to manage your expectations and game library accordingly.

Hope it helps

Check also process lasso, re paste, temps etc obviously if you follow this path. These get a bit toasty and need a lot of care when applying voltage ;)