If you run it as a dedicated server it won't take much CPU, cos its mostly the graphics and sounds that cause the CPU load. Like Mr. Beeblebrox said, probably a P3-700 can easily host a 32 player game. Bandwidth, now that's a different story. I assume U2 will take a bit more bandwidth per player than UT, I guess around 40kb. This means you would need a line that can bear 1.3 Mbit/s synchron.