860 can do sli with 780's (non Ti) but not sure is it enough to do with Ti's.
Id get better psu. and this is better. http://ca.pcpartpicker.com/part/rosewill-power-supply-lightning1000
Id just look this to come on sale with 160$ price.
800w is good too. http://ca.pcpartpicker.com/part/rosewill-power-supply-lightning800
And look here before buy if there is any good deals. http://promotions.newegg.com/neemail/latest/index-landing.aspx