SoA 2 has been constructed almost entirely on low end systems. With the goal of "if your computer can run sins then you can run SoA 2". While i have a dual core laptop with 4 gigs of ram, its video chipset well to put it mildly SUCKS. I rate it about equal to an old gforce 6600. I can play games like supreme commander, but i have to nerf all settings to low, and the newest stuff... forget it. it aint happening.
My big rig is pretty much industrial art, and virtually useless for anything other than web surfing, and playing sins. I keep it because most of my modding programs dont work well in vista, or my laptop (as you will find out if you run vista). Its an amd sempron 3100+, 1 gig of ram, and a gforce 6600gt video card.
You will have to keep most of your texture settings at medium, or low with 1 gig of ram. The advantage of modding on a low end system is that if the mod works well on your rig it will run excellent on a higher end system.
Here is an interesting site if you want to tweak your old box, and get some more speed from it http://www.blackviper.com/
Dont mess around with your settings if you dont know what you are doing.