I need to choose a processor to build my next PC around.
Does any software currently take advantage of Dual Core processors or 64 bit processors?

Can you get Dual Core (Multi Core?) 64 bit CPUs yet?

Bearing in mind that most of the games I play are from the 2001 era.
Unreal Tournament, Age Of Empires etc
Not really requiring anything more than 1GHz and 128 MB RAM

I'm wondering if I really need anything more than 2GHz?
Obviously I want the highest spec'd PC out there but I am very poor at the moment and cant really afford more than £400.