Re: Power Supply and GPU
Don't use that PSU calculator, had I have followed it my PC would not be working.
Answers to questions
1: Yes any PSU should work (with correct wires), PC only draws the power it needs, so technically a higher wattage is better.
2. Any really, just look for a decent priced one that does what you want
3. GTX 550Ti, or GTX 560 if you want to spend a bit more.
In terms of PSU, the 560 will need about 36A on the 12V rail, the 550Ti will need 24A, get a decent 650 or something.