Put every game you want on your wishlist, make an account on https://isthereanydeal.com/ and link your Steam account, and receive a (configurable) e-mail when it’s on sale which also tells you how much it’s been on sale before. Never pay anywhere close to full price again. Except for the indie games that deserve it of course.
A 10 Gbps network is MUCH slower than even the smallest oldest PCIe slot you have. So cramming the GPUs in any old slot that’ll fit is a much better option than distributing it over multiple PCs.