i want to run 2x ASUS GeForce GTX 660Ti 2GB PhysX CUDA
the problem is just that i only have a 750W powersupply and the minimum powersuply for 1 card is 450W
so would 750W powesupply be enough to run SLI with cards who have a 450W minimum each?
The 450w recommendation includes an allowance for all other parts of a normal rig in addition to the graphics card.
The card needs power for two 6 pin connectors, and the pci-e slot, each of which can draw a maximum of 75w each.
At most, you would need 450+225=675w, and likely much less.
SLI GTX660ti is very nice if you want to win benchmark competitions.
But, I really think you would enjoy gaming more with a single strong card like a GTX670 or GTX680 or 7970 which would cost less.
Your psu needs with a GTX670 would be 500w, 550w for a GTX680.
Either configuration will run a 1080P monitor very well.
Consider the single card option.