Ati or nvidia

these are the cards I'm looking at right nowhttp://www.newegg.com/Product/Product.aspx?Item=N82E168... and the http://www.newegg.com/Product/Product.aspx?Item=N82E168... any suggestions would be great  

**EDITED**

If that's the model I found (their site said that model doesn't exist, so I found the one most similar in name), NEITHER card will work in that system, as it has only a 250w power supply.

You have VERY limited upgrade options without replacing that power supply, and even then, you will be very CPU limited (it has an older Athlon dual core), I think that even getting a 4650 would be pushing it on that power supply.

a 4870 is probably the best upgrade due to being cheaper than both of them and equal to the 260 in terms of performance, and better than the 5770. dont get the 5770 for dx11, as it is not powerful enough to make the most of it, and the power savings arent noticeable on your electricity bill.

if your gonna get a 4870 look for a sapphire one, getting a used one is probably a better idea

Well here is another look at my system http://www.emachines.com/products/products.html?prod=EL... as i said before I am going to replace my psu was thinking about the http://www.newegg.com/Product/Product.aspx?Item=N82E168... Thanks for everyones comments. Would like to know if my cpu would be able to handle the 4870 or the gtx 260 with the psu upgrade.

sorry posted the wrond system in the above link my system is actually http://www.emachines.com/products/products.html?prod=ET...