What PC is best to run rFactor 2?

Hamilton, if your ok with it, i would be willing to build your pc and ship it to you if you want. It will save you a LOT of money or you can look at it as getting a LOT more for your money. I did the same for a friend of mine in Holland, he wasn't pc savvy and i offered to build him his pc with custom parts and he saved about 40% compared to pre-built market versions.

Depends where you live as well ofc.

 

From the benchmarks I saw before it seems that RFactor 2 sees some small gains going from 2 cores to 3, but after 3 the improvements stop. Also, hypthreading shows no improvements. So you can rule out any 6-core processors and any 4-core w/ HT processors.

I would go for an intel Haswell CPU. If it's just for racing sims go for the fastest non-Hyperthreading 4-core Haswell. I believe it is the 4670k? They might have a slightly higher clocked version out now like a 4675 or 4680 or something, sometimes Intel does that (like 2600k to 2700k, 3960x to 3970x) etc. but most likely just get the 4670k. The 4770k ispretty much the same CPU but with Hyperthreading which adds nothing to 95% of games, adds $100 or so to the cost of the CPU, and adds 7-10 degrees (celsius) of heat which may lower your max potential safe overclock especially if you are heat limited rather than voltage limited, which you will most likely be with Haswell (especially with the HT chips).

GPU...Get a single NVIDIA GeForce GTX 780 Ti, or a regular 780 (non-Ti). The graphics card makes the biggest difference so unless you're struggling to eat meals then try dishing out the little extra for the Ti.

If you need advice with RAM (speed, latencies, brands, amounts, etc), hard drives/SSDs, motherboards, power supplies, etc. let us know.

EDIT: 400 pounds? Im assuming thats around $700? Buy used. I almost always buy used. 4 monitors, like 7 graphics cards, 2 CPUs, 2 power supplies, 2 different kits of RAM, 1 hard drive, never had an issue with them, never ripped off. Craigslist and Ebay are your best friends, especially craigslist where you have a chance to meet people and test the product before you buy, negotiate prices/deals, etc.

Get a used 4670K and a used GTX780 (Ti model if you can) and you'll be laughing