The PSU is not one I would call "acceptable" and just above the minimum recommended but i doubt that's the problem unless you are overclocking something..
Here is Guru3D's power supply recommendation:
AMD R9 290 - On your average system the card requires you to have a 550 Watt power supply unit.
AMD R9 290 Crossfire - On your average system the cards require you to have a 700 Watt power supply unit as minimum.
AMD R9 290X - On your average system the card requires you to have a 550~600 Watt power supply unit.
AMD R9 290X Crossfire - On your average system the cards require you to have a 800 Watt power supply unit as minimum.
If you are going to overclock GPU or processor, then we do recommend you purchase something with some more stamina.
The BIOS is not your problem.
The card's age won't be an issue, it's already past the half way point as far as "being current".
But here's the key .... "So, I bought an Asus R9 290 DirectCU II graphics card recently. "
What does Asus Tech Support say ? They should guide you thru a troubleshooting procedure ain about 10 minutes.
The cable from monitor to card might be a problem,