There is no reason that the card won't fit the motherboard. Sounds like you are good to go.
Your power supply is running close though. I'd expect that 550W would be enough but just be wary about adding too much more to it.
After this upgrade the next will be my PSU but i was just concerned at the fact that the R9 290x is PCIe Gen 3.0 but my motherboard is PCIe Gen 2.0?