Card upgrade for running 5760 x 1080

SETUP:

MOBO - Foxconn Blackops
VID CARD - Primary HD4850, Secondary X1550
CPU - Q6600 @ 3Ghz, 425x7
RAM - TEAM XTREEM DDR3 1866 @ 1700, 8-8-8-18
HDD - 3x 500GB 7200.12 in RAID 0
OS - Windows 7 32Bit

Ok well i've recently gone and bought my third 1080p moniter but the HD4850 has hit its limit, I wish to game at 5760 x 1080 and am asking if a HD4890 or 4890+4850CF/ would be able to pull it off if not please give your recomendations, also open to nvidea if the have a powerful enough card. Budget maxes at $400

i wish to play games like crysis, fallout 3 and prototype on max settings no AA at this res, my HD4850 did sucsessfully pull this of at 3840 x 1080 but the third drags it down to sub 12FPS,

any help would be appreciated and before its asked,
i modify the config files to run a custom res window, !No interest in SOFT TH OR TH2G!
i know crossfire only allows you to use 2 outputs thats why i mentioned the X1550 my motherboard has 3 pcie ports 16,16,4 third output would be through it
nvideas an option because i have a 8200gs that i could use as a secondary

its 3 seperate moniters, please read before replying,