MSI GX740 with 5870 1gb ddr5

just had a look at this big boy over at xoticpc.
hell they sure do get them out fast

under the hood is a 5870 with ddr5....
and that too at such a sweet price.

my first one was a 1719 (aka gt700 i think) and looking to upgrade.


its little brother was also up online with a 5850 ati gpu.
one question for the gurus out there..
what kind of performance can i expect between the two gpus? say i keep the rest of the config the same, and play the same game (crysis...) at same settings, what kind of difference should there be between the two?

(by the way eta is march...
come on guys u can do better...)