Help to choose 350w-460w PSU that support GTX550ti

http://dynaquestpc.com/index.php/components-2/power-sup...
http://www.hardwaresecrets.com/article/Antec-Basiq-BP50...

I'd suggest the very good Antec Basiq BP500U: http://dynaquestpc.com/index.php/components-2/power-sup... which is on sale for 1800 pesos.

If you want to objectively, accurately and scientifically determine what PSU power is required for your Vid card and PC in both watts and 12v rail amps., the forum Utility link below will show you how easy it is to calculate this information and objectively determine which PSUs are quality built, reliable PSUs that can meet your needs. Be advised that the available 12v rail amps. is just as important as the total PSU wattage. You need both to be correct.

http://www.tomshardware.com/forum/314712-28-please-read...

use this link to find the power requirement for your psu..
http://extreme.outervision.com/psucalculator.jsp
or
http://www.coolermaster.outervision.com/
or
http://educations.newegg.com/tool/psucalc/index.html
based on ur specs i would recommend u to use the third one..buy a corsair or antec psu as they are very good makers for psu but they are little bit costly..if you are on a tight budget psu like mercury or intex will even satisfy ur needs if you are not going to add any graphics card in future these psu are very cheap and have a better quality than street range psu's..