I've never built my own system -- the research is far too tedious, and there are far too many choices to make. I have trouble enough deciding between two alternatives. If I built my own, they'd be almost infinite. 

Hubby and me had two systems custom built. Gack. Never again. I went for 3 years with no sound (not even system sound) -- and no one could figure out why. I think it was at that time that I learned to despise video tutorials. It must be hell to be deaf and on the internet these days. No one even gives a second thought to accessibility any more, not even major corporations -- like Smith Micro.

But if you don't suffer decision fatigue like me, building your own seems like a very good plan. 

When I was last looking for an upgrade to my machine, Dell was having a sale on workstations, and I chatted to a tech and told him exactly which applications I wanted to use the machine for (Poser mostly) and what my budget was, and he came back ten minutes later with a lovely and very fast build for exactly $4001. I'd own it, but my credit card was declined -- I later found out because it was among those stolen in the Sony hack. I never bothered to get that machine because it really was more money than I wanted to spend. But, man, it sure would be nice to have those 12 cores when I'm rendering. 

In any case, I expect you can get something pretty similar if you build it yourself -- and well within your budget.

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PoserPro 2014, PS CS5.5 Ext, Nikon D300. Win 8, i7-4770 @ 3.4 GHz, AMD Radeon 8570, 12 GB RAM.