Lightroom is all about processing power and hard drive speed. The GPU has only a marginal impact on the develop module. PS does utilize the GPU a bit more, but even then it's for a few specialized features and to speed up some processes (blurring, smart sharpening, resizing)
https://helpx.adobe.com/photoshop/kb/photoshop-cc-gpu-card-faq.html
FWIW, I'm a professional wedding photographer who somehow has survived the last 3 years on this poor 2012 quad mini, but a 6-core i7 (+8gb ram with 32gb on my desk to go in and a 1tb SSD) is coming my way! Being able to fly through images, even in the develop module, really just requires a stupid fast hard drive (to quickly read the catalog file, previews, smart previews, and raws if necessary) and some proper LR preparation for speed.
Thanks. Very insightful.
What is your LR preparation to optimize speed?