I would contact PC manufacturers for this issue. It will depend on the graphics card and, up to a point, the OS. You could call Novatech or similar manufacturers, and ask their advice. That way you are guaranteed of the PC being compatible with what you need.
I can't recommend any other as most PCs I've bought have been off-the-shelf as it were. I've built from an empty tower case using their site. Not cheap but pretty good in my humble opinion.