Your computer has an AGP bus, which is very outdated, which, sadly, means you might want to consider upgrading the entire computer, or purchasing something a little more recent.
If that is not an option, here is a link to a card with 4x agp bus on new egg that use a 250w power supply or less. This is the Nvidea 6200 model (and the only option in stock), but there are a couple 5200's in stock as well if you needed to go that route. http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Checked out the card you mentioned at Newegg and it is the correct bus type. However, the data bus on my AGP slot is 32 bit while the card you suggest is 64 bit - will this present a problem if the output is to a digital monitor.
The card listed works in an AGP 4x and AGP 8x slot. AGP 4x is 32 bit and AGP 8x is the 64bit standard. AGP 8x is also known as AGP 3.0. I don't think there should be a problem with this since the card specifies it works with AGP 4x (or 32bit) mode.