I want to build a comp that has a lot of potential, and so gets upgraded every so often to keep up to date
Then you might as well get yourself a multi-cpu server board and fill it to the brim with RAM.
I mean, one can't buy one computer and expect to just be able to upgrade it after years. Just build yourself a new PC once in a while that has power with one powerful graphics card and a shitload of RAM. But getting multiple graphic cards is a waste, especially if you go for price-power-ratios.
Seriously, don't do that.
Heck, I bet for the money of the graphic cards alone you could've bought a current-gen console! Or a next-gen handheld!
If I were you, I'd try to get cheaper hardware by searching online or - even better - ask aquaintances that are partners of computer manufacturers if they can order something for you the next time they order something.
This way, you'll save some money because companies usually get discounts since they order directly from the manufacturers or close partners.
For example, when I was working for a ISP, we were IBM partners and got massive discounts for IBM's server-hardware, roughly 30% I think. We could also order Lenovo-Computers and notebooks with a discount since Lenovo was a subsidiary of IBM.
Also, ask them if they have free stuff like HDDs that you can use.