Is this psu good enough or not?

Is a gx 450w psu good enough to power a gd 5850 or gtx 460/470? The system specs:
Core 2 duo e6400 2.4 ghz
4 gb ddr2 800 mhz ram
Random hp case and motherboard
Random 2.5" 320 gb toshiba hdd
2x dvd rw ( don't know why)
No extra cooling fans off any sort except a stockish intel cooler
This is a machine thats from my little brother and he needs a better gpu now the question is wich one off these is best fit as i can go to someone who sells them for 40~€ a piece
I'm just a bit worried about the psu so can i put one of these cards in there or is it a no go?