Tell him to forget about SLI. A single GTX 460 will already be fantastic for 1600x900, especially when overclocked. Only consider a second if he is going to upgrade the monitor to at least 1920x1080.
As for the i5 it should be fine but why only OC to 3.2ghz?
He mentioned SLi because he doesn't want to build a whole new computer later on for when a new more demanding game comes out. He figures he could just use one GTX460 card now and when he needs a stronger GPU, he'll add in another 460 and complete the SLi to play the next level games without buying a whole new computer.