As another poster has commented, comparing Intel processors across the generations can be dangerous.  Being that the main thing you're looking to do is run high-powered SDR software, I'm afraid you cannot do it on the cheap.  SDR-Radio is a quite intensive program simply because it has to be.  It's processing 2Mbps or more of data, running gobs of Fourier transformations, etc.  That's why CUDA is so important as the deep computational algorithms are offloaded to the GPU.  

You mentioned an Intel Core i5-4570.  That is a processor from Q2 2013, so it's six years old.  From the 4 in the model number, you know it's a 4th generation variant.  Intel is currently shipping generation 9, although that's relatively new.  Generation 8 chips are still being sold across all manufacturers.  As a general guideline, for doing heavy math, you should not go more than one or two generations back.

A CPU from 2013 is just not suited for top-end software from 2019 like SDR-Radio.

The CUDA/GPU benefit is significant, but you can get around it by paying in CPU usage.  I have one computer with a Nvidia GPU and CUDA and a Microsoft Surface, which uses Intel graphics.  When I run SDR-Radio on the machine with CUDA, I barely know it's running.  When I run it on my Surface, I'm generally around 25%-40% CPU usage, depending on how much data (bandwidth) I'm processing.  It's not a sin to have moderate to high CPU usage, and I'm not affected in my other work.  But I do take a significant hit by not having CUDA.

If you want the best for SDR-Radio, buy a modern CPU (look at an AMD Ryzen) and absolutely get a decent video card.  I wish you the best!  I realize that isn't the answer you're seeking.  

-- Bob (N3OEA)