Psu + graphics question

so as of now im preparing to build a computer hopefully in the next couple of weeks but im still not sure what psu to get

right now im looking at a OCZ Fatal1ty OCZ550FTY cuz its extremely cheap as of now (<$50)

right now im planning to buy a radeon hd 5670

the question is: if in the future i plan to upgrade my graphics should i crossfire (and is my current psu good enough?) or should i just buy a new one and replace it later?

current build (but always looking for advice to make it cheaper or perform better)

phenom ii x4 955
MSI 890GXM-G65 AM3 AMD 890GX
G.SKILL 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600
Thermaltake V9 Black Edition
COOLER MASTER Hyper 212
SAPPHIRE 100287VGAL Radeon HD 5670 (Redwood) 512MB
OCZ Fatal1ty OCZ550FTY 550W

thanks