Thanks Guys. It's good to see the answer and concerns from both side.
I just got the PSU for 2 weeks, not in a good position to sell. I was planning to CF R9 270/80/X when I got it. It's great value and just enough for all I need.
However, I got a killer deal for the pair of R9 290s for only $500(1 new, 1 near new) last weekend, couldn't miss it... love their LED lights.
I thought it should work, but just not sure if it's tooo much. Hope it's ok, since I don't play long hours on full load (Max 2-3hrs a day)
Hopefully not giving much damage to PSU till my next CPU/RAM upgrade next year. Really wish the next CPU generation can be lower power demanding