More aboutathlon 860k 7ghz sapphire 250 gddr5 128bit compatible asus a55bm
As long as you use an FM2+ socket motherboard, the CPU will work.
PCI-express devices (like GPUs) are generic today. As long as you have a PCI-Ex 16x slot, it will work (when you install the drivers, of course).
RAM, DDR3, no problem.
as long as the motherboard is compatible with fm2+
Yes the motherboard will accept both the 860K and the R5 250. Only thing is you will need at least BIOS 1901 to get the 860K to work with the motherboard. There's a tiny chance you might be able to boot with the CPU without the required BIOS to flash to a new BIOS but I highly doubt it. Most people who bought an 860K had a problem with needing an updated BIOS, which you can't update/flash unless you have an older FM2 APU.