Assuming you can reuse your RAM?
My basket at Overclockers UK:
- 1 x Intel Core i5-10600K 4.10GHz (Comet Lake) Socket LGA1200 Processor - Retail= £218.99
- 1 x MSI Z490-A Pro (Socket LGA 1200) DDR4 ATX Motherboard= £149.99
You could save £60-100 by dropping down to the 10400F if you're not interested in overclocking. I'm not 100% clued up on Intel motherboards so should you go this route I'd ask for second opinions on the mobo.
AMD:
My basket at Overclockers UK:
- 1 x Gigabyte B550M AORUS ELITE (AMD AM4) B550 Micro-ATX Motherboard= £89.99
- 1 x AMD Ryzen 5 5600X Six Core 4.6GHz (Socket AM4) Processor - Retail= £329.99
Alternatively you could save £140 + by picking up a 3600 instead of the 5600X, honestly at 1440P or above you're probably not going to notice a difference. If you do go AMD you might want to consider your RAM, even if you already have DDR4 Ryzen very much likes and needs fast memory to see the best results. Ideally you want 3200 as a minimum, although if you're on 3000 you'll be fine -- if your RAM is slower than that you could see if you can OC it.
The above are both 6c12t solutions, you could probably fit 8c16t into your budget, but whether or not it's worthwhile is another matter.
With the AMD option you have a better platform and easier future upgrades, it's the route I would go personally.
Wow thanks for all that, but my fault I ment 400 just for the CPU, I have about 600 budget, approx 200 for a Mobo and 400 for the CPU, sorry for not being clear.