Yeah, Alan Wake is heavily multithreaded, meaning you'll need a dual-core for quad-core to run it. It might be possible for single cores, but you'll probably get waves of lag even on lowest settings.
I think I'll wait two more years before I upgrade to 45nm with Intel's Nehalem core.
2008 baby! Becides, I'll probably buy an Xbox 360 and seeing that Alan Wake is Games for Windows and Xbox 360 exclusive...