What budget.....absolute maximum for ALL parts?
Where will you buy.....country and vendor?
With a platform that old, you'd likely want new motherboard, CPU, and RAM at a minimum.
Possibly more parts than that.....power supply, cooler, drives?
Can you spend 500? 800?
Newegg says Intel 8 core CPUs begin around 220.
Newegg says recent generation Intel CPUs (socket 1700) with 10 or more cores begin around 200.