I recently got my little "monster".
For "small" sets you can try the nVidia GTX /RTX cards with 8 to 12 GB GPU RAM.
If your scene needs more memory, you have to render with the CPU. So it should be a quick one. 12 to 16 cores at least.
Due to the costs I created a "small" setup with Asus GeForce GTX 1060 6GB and the AMD Ryzen™ Threadripper™ 1920X.
For my needs its good enough. 2-3 hours for my latest renders (3000 x 3000 pix).