Unfortunately the EVGA and Super Flower units have not yet been released, so you'll have to wait if you want those two.
Continuous means that the PSU is capable of delivering 1600W at all times, not that it actually always draws 1600W at all times.
 
I'd say you need 1250 to meet spec, considering 250 per card plus overhead. That Hercules is a Tier 3 PSU, stay away from it for extreme usage which I would definitely consider 4 290's extreme. You'd be better off with the EVGA which is a known quantity with a reliable reputation or the Corsair which has great reviews, for, well, a Corsair PSU. Guess they finally found a good oem.