I've been getting very high framerates with my system with most of the details turned almost all the way up, and 1024 textures at 1280x1024 resolution and 2xQ FSAA. It's very smooth most of the time. If I was into mud moving and base attack I'd probably reduce or adjust some of the detail settings to try to get max framerate at smokey airfields, but my system just doesn't chug badly enough for me to want to do that. It's not perfect, but I only spent about $1000 on the critical components of memory, cpu, vid card, and mobo.
I have no hard evidence that an intel system would be better or worse, but the athlon 64 roundly stomps the intel cpus in pretty much every single game review I've ever read online. Even though they didn't use AH2 for the benchmarks, the cross section of games used was wide enough that it's reasonable to extrapolate that dollar for dollar, the AMD cpus are better for games than the intel cpus, and the fastest AMD cpu is better for games than the fastest intel cpu.