Hey guys I did some benchmark on my poor second rig
AMD Phenom II x4 955 BE (stock)
Asus EAH5670 1Gb overclocked
Resolution 1280x1024 75Hz
4Gb Ram 1600Mhz
So I played some blood money mode and drove a bit with a motorcycle and run and shot guys with a shotgun :D
FPS: Avg: 35.382 - Min: 30 - Max: 42.
So you can play low with that kind of rig Battlefield hardline and with good fps above 30 :)