Well ... I did a quick and dirty configuration check with this budget, and it's there : https://www.pcspecialist.co.uk/saved-co ... GRjWXV7tE/
Bear in mind that :
1) I always mount my computers myself. It allows me to get the best prices possible by choosing the cheapest vendor for a given hardware element. Plus it saves the cost of mounting. If you can do so, this configuration will likely cost you less than 600£.
2) I had to do some sacrifices to lower the price tag. These sacrifices are :
- RAM. RAM is ridiculously expensive these years. Even if it has started lowering a little since the beginning of the year, it's still around twice what it was 2 years ago. For a gaming rig, I'd suggest 16 GB DDR4 3000 (2x8) I sacrificed speed and quantity, but took a 1x8, so that you can add another 8GB later on
- CPU : I chose an i3-8100 instead of the i5-8500 I wanted. If you can afford the i5-8500, it would be a better choice.
- GPU : thanks to (because of) cryptocurrency mining, video card prices are consistently high. I'd rather have chosen a 1050 Ti (4GB) or a 1060 (4GB) instead of this 1050 (2 GB). Not for Factorio, but for other AAA titles, that would benefit from a higher GPU.
- small-ish disks. I'd have preferred a 250 GB OS SSD instead of this 128 GB, and a 2TB HDD instead of this 500 GB. But everything comes at a price, right ?
The first configuration I tried was more around 900-ish£, so I had to tune down.
I purposefully chose a good (thus expensive) PSU (People often underestimate the benefits of a good PSU). 80 Plus Gold will get you good savings on power, and a high enough maximum power will ensure your PC will be used in the most efficient range of your PSU when on high load. I eyeballed to 250-300W peak consumption of this configuration, which should pu you clost to 50% load on the PSU, so 90+ efficiency. More info and math here : https://outervision.com/pc-energy-cost.
All that said, making a computer is no science, every one will have one's preferences. ATM, I'm not convinced by AMD CPU&GPUs. They have gotten better than 2 years ago, but for gaming purposes, I think they are suboptimal. Things may change, so I keep an eye on this.