It does say, and I quote...
" Acer
All the power you need."
:lol: :lol: :lol:
I doubt that mind you! :? :D
In all honesty Nflight without knowing what PSU is in there it would be a bit churlish to order an additional PSU. If you are going to upgrade the graphics card only then you may find it has sufficient power it is always best to phone the supplier to find out - if it has the standard OEM <=320W PSU then you're probably right to order something with a bit more juice to be on the safe side.
However you could order an FSP Booster X3 which slots into a drive bay and supplies a dedicated 300W to the graphics cards, cheap and easy setup.
http://www.overclock3d.net/reviews.p...3_300w_12v_psu
Else, if you really feel you need a new PSU then aim for >=500W so I would go for something like this
http://www.newegg.com/Product/Produc...82E16817153028