Your either gonna have to spent alot more if you stay with MSI, only their top of the line board
790i has 2x x16. Get an EVGA 680i A1 board, only $50.oo US more than the one you have.
It's a popular board and on back order on the EVGA site, but probably can find one somewhere.
But don't get the T1, it's the older brother to the A1 and had problems from the get go. They
replaced every board they sold and paid all shipping costs, it was that bad. And I think the T1s
on the market now are just the old ones but fixed. You got plenty of computing power, but you
gotta get the cards working to their potential. That's about typical pricing to go high end SLI, but
way better price than a store bought one like alienware. Good luck, and give a shout when you
get it all working!  8-)

PS: just look for the Nvidia SLI certified sticker on the mother board box or advertising. If it's
certified it's 2x x16.