Do i need a new PSU?

[yogurt]

Hey guys Im buying a new graphic card and im wondering if i need a new psu to support it .
My current PSU is a Antec BP550 Plus, 550W.
What im planning on buying is a Ati Radeon 5850 OEM 1GB GDDR5. and i currently have an xfx radeon 4850 1gb ddr3

cpu: AMD Phenom II x4 840
mobo: GIGABYTE GA-MA785GM-US2H
ram:4GB OCZ DDR2 1066 mhz (2x4)
Cpu Cooler: stock
Case: antec 300 ( 3. 120mm fans, 1. 140mm, 1. 80mm fan)
HDD: 2 255GB 7400rpm HDD's Raid 0

Please help

 

[Indigo]

The Antec 550 should be fine. AMD's site suggests 600 watts or more for CrossFire, and 500 for single card operation.