How big of a PSU do I really need?

[ewoglightstar]

System specs,

Cooler Master 500w PSU - a couple years old
Gigabyte Z68X-UD3H-B3 Motherboard
intel i7 2600k processor
Sony DVD RW 22x
Western Digital Caviar Black 1tb
4x 140mm fans
2x 120mm fans
stock CPU Heatsink and fan
4GB(2x2GB sticks) Patriot Viper Extreme DDR3 2133 MHZ

I think my current PSU isn't big enough because sometimes the screen flashes black when things are running full screen. I am currently using the built in video card on the motherboard but will be getting a nvida GTX 550. So how big of PSU do I need??

Note: I used the calculator on http://extreme.outervision.com/PSUEngine and it said I need a 482W PSU...

 

[DrAwesome109]

For all that, you'll probably do best with a 600w or higher. I'd do 700 or 750 to be safe. Corsair, Rosewill, OCZ, and XFX all make great products.

This one has free shipping with a nice rebate offer going on right now.
http://www.newegg.com/Product/Product.aspx?Item=N82E16817139020

 

[geofelt]

The graphics card is the prime contributor to psu requirements.

EVGA has the following recommendations for psu's:
GTX550ti needs 400w with 24a on the 12v rails plus one 6-pin PCI-E power lead.

GTX560 needs 450w with 24a on the 12v rails plus two 6-pin PCI-E power leads.

GTX560Ti needs 500w with 30a on the 12v rails plus two 6-pin PCI-E power leads.

GTX570 needs 550w with 38a on the 12v rails plus two 6-pin PCI-E power leads.

GTX580 needs 600w with 42a on the 12v rails plus one 6-pin and one 8-pin PCI-E power lead.

GTX590 needs 700w with 50a on the 12v rails plus two 8-pin PCI-E power leads or 4 6-pin power leads.
It assumes a normal complement of cpu, overclock and peripherals.

Assuming your 500w psu is sound, you should have no issues with a GTX550.
I don't think the screen issue is related.
Look first to update your integrated display driver.
The other possibility is a failing monitor.