I have 2 Sapphire 7970's and 3 ASUS 24" screens running in eyefinity these Monitors are running from HDMI ports and I have them setup like this :-
Monitor 1 HDMI to DVI
Monitor 2 HDMI to DVI
Monitor 3 HDMI to DVI to an Active Display port adaptor
my Res is 5924 x 1080
Remember to connect all 3 monitors to the top card.
I have no speed issues at all when running cryisis 3, BF3 etc.
I Know im in the UK and may not help you but im using this one so maybe you can look to see if you can get this one :-http://www.overclockers.co.uk/showproduct.php?prodid=GX-058-HS&groupid=1929&catid=1757