I agree about the site being inaccurate, but it is the best calculator out there unfortunately. I would recommend getting a PSu larger than you need, due to the effects of capacitor aging. For that build I would recommend this PSU:http://www.newegg.com/Product/Product.aspx?Item=N82E16817139028
It has plenty of power to allow you to upgrade other components later. There is a 500w version for $10 less, but I find it kind of pointless. In general, it is recomended that you buy PSU's made by Seasonic, Corsair, antec or some of the XFX PSU's.
I would also try and spend a a little more on your graphics card if this is to be a gaming rig, try for at least a 650ti:http://www.newegg.com/Product/Product.aspx?Item=N82E16814130838&nm_mc=OTC-pr1c3grabb3r&cm_mmc=OTC-pr1c3grabb3r-_-Video+Cards-_-EVGA-_-14130838
The toms hardware GPU hierarchy chart should be helpful to you in this area:http://www.tomshardware.com/reviews/gaming-graphics-card-review,3107-3.html
Which i5 do you plan on getting, and what motherboard?