Simple question.  Do I spend the money to do dual core technology or not?  I usually keep a computer four years or so.  I definitely want 64 bit.  I do write multi-threaded code from time to time so it would vey cool for that, but for the most part I'm surfing the web and doing mail.  I do run a small site on my computer.  

ETA:  Should I buy the cpu/motherboard combo?

I would say yes.  It certainly can't hurt.

you run a website off your PC....ohhh k.

If funds permit go with an AMD dual core.  If not get a single core one on a MB that will accept the dual core as a drop in replacement later on.  Since you are going to ask about RAM sooner or later my rule of thumb for modern computing 2 GB per CPU.  So a dual core machine would get 4 1 GB sticks.  I run Win XP Pro X64 bit edition and it loves RAM and will take all you can through at it.

Quoted: you run a website off your PC....ohhh k.

It's not much.  Mostly use it for testing.