Alienware Aurora Power Supply Unit

Hi guys.  I recently purchase the Alienware Aurora, specifically the featured promotion you can see here (not sure if links are okay, but it's to Dell's website) http://configure.us.dell.com/dellstore/config.aspx?c=us&l=en&oc=DPDODZ1&cs=19&kc=9&X=9&Y=6

The power supply unit comes with 875W of power, but that can be deceptive.  From other Aurora users, I've pieced together that (in all likelihood) the PSU uses six 12 Volt rails to supply 18 Amperage apiece.  Since a component can't connect to more than one rail at a time (but can vice-versa), that only leave 216W output for each of the HD 5770 cards that my config comes with in Crossfire.  Checking stats, it looks like each card takes up to 280W at peak stress, which would be far too much to operate here.  Had a terrible time yesterday talking to Dell Support (and Alienware support, not sure I've ever been treated as poorly by a manager as I have by theirs), and a slightly better time today talking to someone named Kyle S who did his absolute best.  It would seem silly to send a unit that would be dead on arrival (or would overheat as soon as I played something intensive on max settings with 4xAA), but I've seen other horror posts of people saying they received units that the config wouldn't work upon arrival, so I'm a little concerned.

Does anyone know know whether the 875W PSU included will adequately (and I mean up to peak stress, not medium settings) the dual 5770s?  Or if not, where I can find a PSU that will plug into the Alienware? I saw Methodical talking about a 1.2K PSU, but didn't know the specifications or if it would plug into the Aurora without losing functionality/rewiring the whole thing (comp in question was an Area 51).

Thanks for any help.