I'm in the same boat there Ryno. Having just looked at a couple of CPU hierarchy sites, the old 4790K still holds up pretty well against current mid-level i5 CPUs - and it's certainly above the minimum spec - so should be ok!
I was just looking up a comparison to the recommended i5 chip, and it looks like my i7 is about ~15% slower than that one in real world tests. I guess the difference will be in how ACC deals with cores/threads. If it uses them all then I might be OK. I'm a VR junkie now, though, and I like running in large fields. I run races with ~40 AI at Spa in a mixed GT3 class (every Kunos GT3 plus a few mod cars, and a couple BOP'd GTE cars) quite often, and I can't maintain 45FPS in some spots on the track and sometimes get the 100% CPU warning.
Maybe I'm just greedy