PSU requirements for new GPU's?

[CaldabOg]

I was checking out some of the new cards, (currently have 8800 gts 512), and noticed that on like the gtx 260 and 275 that I was looking into, there was a PSU requirement of at least 550w, which suprised me. The PSU I have is a 535w unit and the only peripherals I have are 1 HD, 1 GPU, X-Fi card and DVD burner.

So, I'm wondering, if i want to upgrade my video card do I really have to upgrade my PSU as well? Are the new GPU's that power hungry?

Thx in advance ^^

 

[CaldabOg]

It is an Enermax EG565P-VE 535w. And another thing I have no clue about is when a PSU has 1 or multiple 12v rails, I have no clue what that means or what the advantage is. Mine said it had 2 12v rails when I got it.

I am also going to upgrade from an original E6600 C2D to a Q9550 and a new MB, I'm assuming I would be ok on that upgrade with my current PSU?

thx again 8)