What is more important for faster processing time, CPU or GPU?

So currently I have a i7-7700K CPU and a Geforce 1080Ti 11GB. If I want to cut down the time it takes to process a video that is being upscaled, what should I upgrade, GPU or CPU?

I will upgrade the CPU and leave the GPU upgrade for later.
I have a i7-9700K and a RTX 3060Ti and the bottleneck here is the CPU.
Source 1080p to Proteus only to do it’s magic without upscaling… 4.3fps
Screenshot 2023-06-19 145508

GPU would come first for order of importance, however, often time, replacing the entire machine is the more economical option and ends up being the better choice down the road. The 1080ti is an entry-level device for our purposes. I would check out the benchmarking post that @Carlito shared