Looking for some desktop PC advise (new purchase)

I don’t see anywhere in my original post about a budget basis. Although I’m not looking to spend unlimited funds, I’m not going to be cheap either. That is why I have the turd that I want to replace. It was cheap (free) from work. It has lasted me 3-4 years though.

What are the differences between the different processors - AMD/Intel/Core/Core 2 etc?