Challenge with these bigger CPUs are not as much filters, if you are using -2s variants. But the challenge are modulators. GPU can help with filters, but not with modulators. With my i7-7700K that is only quad-core, using RTX 2080Ti helps because it frees up CPU cores. But with 8-core CPU like i9-9900K(S) it matters less. So, while the GPU is useful for getting wider selection of filters available for those rates, modulators are the critical aspect here and thus CPU performance.
i7-7700K with help of GPU, and i7-8086K without can do DSD1024 using DSD5 modulator. But ASDM5 gives a drop-out every now and then.
If you look at benchmark figures, possibly single thread performance of LAME MP3 encode benchmark is most representative of relative CPU performance for HQPlayer-type workload.