I'm running a well-optimized 2014 Haswell I5-4590 system with a Radeon 7800 XT in my virtual pinball cabinet. It's handling real-time 3D at 1440p 120fps at medium-high settings and VPX is pretty CPU heavy. My system is probably only a generation or two ahead of the one described (although it's true that Haswell was one of those occasional Intel generations that became legendary for outperforming and generally aging very well).
That's very lopsided in favor of the GPU - if VPX is more CPU intensive that the average video game you could probably swap the 7800 xt for something much cheaper and get the same performance.
Yes, I agree. I was actually planning to retire that mobo and CPU after the GFX upgrade but that damn Haswell is so good, I didn't need to. The previous GFX card (a 1080) was the bottleneck getting 120fps reliably. I really didn't expect the i5-4590 to keep up with 120fps at low latency but got surprised.