PSU help?

[KaiserDragon]

Hi, I bought a PSU when my old one failed, and had it installed in a repair shop, only trouble is I am planning on upgrading my GPU (from a Radeon 7850 to a Radeon 6990) and the wattage goes from 130 up to a rather large 375 and I was wondering would my current PSU be able to handle that? and this is where I run into the problem...

My case is an Antec 300 and the PSU is on the bottom and the sticker detailing the watts is facing the wrong side, I literally cant read it without dismantling my computer so I turn to you, to tell me what PSU I would need with the following spec:

i5 2500k 3.3GHz
Radeon HD 6990 4GB
8GB RAM
2x 500GB HDD

I think I have a 550w PSU but it might be as low as 500.

 

[KaiserDragon]

Unfortunately my PC broke during my university course so I had to repair it asap (can hardly study IT without a computer lol) so my dad paid for it at the time, and I paid him back gradually.

He doesn't keep receipts :/

EDIT: its a Coolmaster PSU which isn't highly recommended but I was desperate at the time lol.

 

[KaiserDragon]

Problem solved! Friend who is upgrading the GPU is also upgrading his 750w PSU to a 1200w so his is going spare, he let me have both for £120 ^^

Thanks to all for the help though, it is appreciated!