I will get a second 8800GTX in order to make a SLI rig.
I'm not sure about my PSU, if it's up to the task.
It's a Spire 600W. ( http://www.spirecoolers.com/main/product_detail.asp?ProdID=551 ).

Some advices ?
;)

That Spire PSU doesn't look very promising, also where are the amps per line info?

I'm using a Corsair HX620, best I've ever used, no sweat with two heavily overclocked 8800GTX's and Quad Core at 3.6Ghz, fully loaded with drives and 4 sticks of Ram (4Gb) :)