Ah, so were you looking at making a gaming and/or workstation pc that looked like a new mac pro and had equivalent or better components if I am understanding this correctly?
The video card is a custom job it is kind of like a W8000 with a 384 bit memory bust like the W9000.
Either way, this part is custom and does not have an exact equal.
A bit of info on the cpu can be found on Google.
Round cases may be more hard to deal with.
You could build a nice ITX work station with a single video card and make a case to look similar
Without the resourced to make such a custom board and cooling system, it is out of all but the most extreme modders abilities for now.
But then what is the equivalents?