I wanted to update my 7+ year old PC (an HTPC with an i3-4130T in an Antec ISK 310-150 case, a pico-PSU, and loads of 2.5" and 3.5" disks crammed in), especially to finally get a GPU, but didn't want to go too big either, and had set myself a £700 max budget. I went for secondhand parts for most of it, mostly for budget reasons but also partly for environmental reasons. I waited for good deals on eBay, and settled for a budget case, the SG13, which works really well - but feels big compared to my previous one! All prices on the left were actual purchases.

Overall this isn't the most impressive build ever but it feels balanced and it's quiet enough. I was worried about noise as I'm going from 1 fan (stock intel from 2013) to 5 (CPU, case, PSU, 2xGPU). Unfortunately the GPU fans remain at 40% on idle, but otherwise it's OK.

A few notes on the choice of parts:

• Advice: Apart from trawling sffpc, I was inspired by Optimum Tech and techbuyersguru.
• Cooler: The Noctua NH-L12S is brilliant in this case with an SFX PSU, but I had to bend the pipes a bit to fit over the RAM, even though this RAM isn't very high! It arrived from the seller with bent pipes anyway, so I wasn't taking many risks. It's a HUGE improvement in noise levels compared to the stock AMD Wraith "Stealth", which isn't stealthy at all.
• RAM: 1 stick of RAM only as I'm waiting for a good deal on a second stick. I'd like 32GB as we are several people using the PC, leaving tons of open tabs and docs, and I don't want to close it all for gaming. I know it's missing dual-channel but it doesn't really matter for everyday tasks.
• Storage: I was aiming for the SN550 and then the SN750 appeared at my target price (new!) so why not.
• GPU: I was hoping for the 1660 Super, but at my price point it wasn't realistic, so settled for the 1660, which still has 6GB of VRAM at least.

Some notes on the assembly:

• Cable management: I was inspired by this thread, this build and these tips. It's a bit hard with the SF450 Gold cables as they are quite stiff but there's a nice flow of air in the end.
• It's become seriously easy to assemble now with NVMe storage... so few cables!! I'm loving it. And I haven't even used the bottom M.2 slot (yet).
• The Noctua cooler was a bit fiddly to install, and once in it became harder to plug the HD Audio and some other connectors. Nothing too bad.
• By far the worst in this process was changing coolers. I had installed the stock AMD cooler, and when it came to changing it, it came up... with the CPU stuck to it 😱😱. I've been VERY lucky as there were no bent pins and it still works, but what a fright... It came unstuck with the help of a wooden ruler in the end. Phew.

I have detailed my process a bit more on this thread.

Apologies for picture quality, I can only build once the kids are asleep so there's little good light.

EDIT: I did some tests to see which fan configuration works best. TLDR: case fa as exhaust, CPU fan pushing up.