Upgrade of Graphics Card for Gateway SX2800-07

I have a Gateway SX2800-07 computer and I'm looking to upgrade my graphics card so that I can play Diablo III and Torchlight 2.

For Torchlight 2, the minimum requirements for the video card is:

Video Card: DirectX compatible 3D graphics card with at least 256MB of addressable memory.
DirectX®: 9.0c


The specs for my computer are:

http://reviews.cnet.com/desktops/gateway-sx-2800-07/450...


Please note that my computer has a 220 watt power supply.


I would prefer to only upgrade my graphics card, if it is possible.


I think I need a low profile graphics card.


Any help would be greatly appreciated!


Thank you in advance!


Thothkristen


Edit: The following discussion (http://www.tomshardware.com/forum/307786-33-watt-profil...) suggests that the Radeon 5570 would work in a similar computer. Also, it claimed the card can't use more than 75 watts. Does my system use 145 watts or less in power or how can I check to see how much wattage it is currently using?

Below are two links for two different Radeon 5570. If this is a suitable card for my computer, do I have a reason to prefer one or the other and if so, which?

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

http://www.newegg.com/Product/Product.aspx?Item=N82E168...