Best core speed processor

I'm looking for a decent processeor with good single core speeds. I'm using some legacy software at work that does not make use of multi cores so looking for best options to speed it up.
Ideally the PC would need to be from HP as they are who we use currently.

i7 7700k or 8700k is good for single core speed but they dont come with cooler so you will have to spend another good $50-$100 for a cooler unless you already got a cooler ready.

For amd, the the ryzen 7 2700x is about 5% slower than the 7700k and cost about $10 more but it comes with a cooler but it should get the work done.

but depending on your budget, there are cheaper cpu. the 7700k and the 2700x is about $305-$319 price range, the 8700k is about $350