Would help to know the rest of your system it all depends on how many harddrives you have what cpu fans watercooling are you overclocking, all factor into your power usage. As long as you are not running a huge RAID array on your average system that will be more then enuff power to run them.
this is the system im building GIGABYTE GA-MA790GPT-UD3H AM3 AMD Phenom II X4 955 Black Edition there is 7 fans in my case Kingston HyperX 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 3 of HITACHI Deskstar HD31000 IDK/7K (0S00163) 1TB 7200 RPM 32MB Cache And yes i mite over clock the 955
Unfortunatlely the power supply will deliver a maximum of 44 amps divided amongst the 4 rails and no more. Although each rail lists 20 amps that is the maximum before sharing will occur. While most virtual rails have circuit protection to shut down at the listed rate this one will share whats available allowing any rail to exceed the 20 amps listed. However there is still a 44 amp limit on the 12v side, this is before subtracting whats being used for the motherboard and other devices so there's actually less than 44amps left for the video cards.
My vote is no it cannot crossfire (2) 4850 dual gpu cards at least not under load for very long.
I personally like the Corsair but it cost more. The problem with the Antec is that it is oversized. If you can fit the Antec and want to save $20 go for it. If you want to have an easier time fitting it in and what I would consider a slightly better psu go with the Corsair.
A note on your setup, be sure to get the 955 with the c3 stepping because it overclocks better and produces a little less heat. I have heard that the heat sinks that come with the 955 are a bit loud and overall not that great, so pick up a good heatsink.