For a system using a single AMD Reference Design Radeon HD 7870 graphics card AMD specifies a minimum of a 500 Watt or greater power supply. The power supply should also have a combined +12 Volt continuous current rating of 27 Amps or greater and have at least two 6-pin PCI Express supplementary power connectors.
Total Power Supply Wattage is NOT the crucial factor in power supply selection!!! Total Continuous Amperage Available on the +12V Rail(s) is the most important factor.
The computer modal is Asus CM6870. Won't any video card fit aslong as it's pcie?
yes pci-e cards are universally fit. but its not motherboard to video card compatability one should look at. its case to video card, as pci-e isnt going away for a long time.
a very crude analogy is like an engine is compatable with all the right mechanical parts, which are universal to some extent. the problem isnt the engine to like wheel compatability, its the engine to frame compatability, and the frame is the computer case.