The WAR people have said in many interviews that you will not need a hot-rod computer to play.
I will probably buy a new midrange card for WAR when it comes out, here is a sweet roundup at Anandtech.com
AnandTech: The Radeon HD 4850 & 4870: AMD Wins at $199 and $299
These guys are REALLY detailed... sometimes I don't know if they make decisions easier or harder, lol!