AMD Ryzen 5 5600G Desktop Processor with AMD Radeon Graphics - £107 (cheaper with fee-free card) @ Amazon Germany

Rx6600 should be an inexpensive upgrade that can handle everything in 1080p on the budget. It dropped close to 220£ mark recently. If you can stretch your budget to mid range then 6700xt is a decent choice, you're looking at around 360£. Go to youtube, type your CPU + GPU + benchmark of your choice and you should see what kind of performance you can expect. (edited)

I might be wrong but You will have a hard time finding a cheap b450 mobo that has 2 display outputs allowing you to run 2 monitors unless you run your monitor on DVI, the ones that do, cost as much as b550. Is there a particular reason you're after ATX board? mATX ones normally more than ample for most unless you need so many PCI slots. Lots of choice for around 80-90£. Can't post particular links as companies are not allowed on HUKD. When you search for one make sure you look at scan, ccl etc too as they often have some decent deals. (edited)

Realistically a B550 or X570, so you have PCIE 4.0. No upgrades possible beyond that

Purchased in Aug 2021 for £238 on Amazon. That was prob near to most expensive it's ever been. Dropped kinda a lot since then as can be in today's prices. Has been a gradual decline.

I bought this cpu at launch and it was a monster a 16 core cpu it made Intel scared to death a year later came the 2700x which was hardly any better. I waited and bought the 24 core 3900x and a MSI meg ace board which was the better part of £400 and now I'm debating either getting a 5900x or a 5950x and making the best of a expensive rig or calling it quits for a full new build. So I know where you are coming from, my son is still using my old 1700x and it's still fine. The 1700x is a 1st gen ryzen most 1st gen boards will run a 5 series ryzen with a bios flash but that makes the bios like a old school bios as it doesn't have enough space on the bios chip so to make it work with 3 series and up so if you do have a 1st gen ryzen board be aware you may have issues with stability and stuff.

The 1700x is still a powerful chip that was around £500 at launch but doesn't support some new stuff but unless you have a specific need me personally I'd stick with what I have and save my money till next gen ryzen probably the 8 series and just upgrade the lot you would of certainly had your money's worth. That's my issue either stick with a very powerful cpu or upgrade to the last am4 cpus although this is a great price I don't know how they would compare as your 1700x has 4 more cores, it all depends what you use your rig for I suppose.

You need to check the motherboard spec. Using the igpu, the maximum I've seen is 5120x2880@60hz on displayport and 4k@60hz on HDMI. (edited)

Yes

It will work

pangoly.com/en/…ard

Have a look on here based on your needs

Paid that for a 5700x...