Too bad I just sold an 7700k and 7600 in the last 6 months.
If you want to push your budget a smidge you could get a new motherboard and CPU for that money. I would recommend a B550 board and an AMD Ryzen 3600. The cpu is around 170-180Euro, plus the motherboard around 100-150 Euro.
Unfortunately the prices exploded recently, probably because of Christmas? Depends on how urgent it is.
Old i5 or i7 7 series cpus are still sold for around 100 euro (my 7700k sold for 150Euro, the 7600 for 90Euro). I feel like that money is better spent if you wait until after Christmas settled down and get a new mobo+cpu or maybe a good combo deal. The B550 even supports the newer 5000 series AMD cpus so prices will probably drop over January-February, or give you a good upgrade path in maybe 3-4 years.
Just my 2 cents, otherwise Raven already showed you the right path. Right now is just the worst time to upgrade as everything is inflated in price, and lots of components can’t be bought as they are out of stock, skyrocketing prices on any pc hardware.