400w Low Profile Power Supply?????

Im trying to find a low profile 400w power supply for my dell C521 and I really cant seem to find anything. Does anyone know where I can find one that isnt 2 expensive? I found this but I cant find out if its a a low profile or not. I dont think it is by the looks of it.

http://accessories.us.dell.com/sna/...e_bnrank=0&baynote_irrank=0&~ck=baynoteSearch

 

Or would it be possible to buy this power supply?

http://accessories.us.dell.com/sna/...e_bnrank=0&baynote_irrank=0&~ck=baynoteSearch

remove the one and have the new one just sit outside the case? Ill have it locked up and what not so no one will get near the wires. But im just curious to see if it would be possibly for me to have the power supply sitten outside the computer. Does it have to be inside of it?

 

Actually scratch all that. Can someone just find me a decent graphics card that will run on a 280 watt power supply lol? Im sorry for posting so much im just a bit flustered.