quad core?

So im building a new computer soon and i need your advice. I have up to £1200 (english pounds) to spend on the base unit, im going for the following:

750 gig hd space min(seagate)
2 gig ram, corsair ( speed dependant on remaining cash)
320 gig 8800 geforce probably

The real question is should i go for a quad core? is it worth spending 500 pounds on it or should i stick to a nice dual core.

It would cost over 300 pounds for the 2.67 dual core (intel), for 200 pounds more i could get the 2.4 quad core, then it would  still be an above average system in 3 years time.

Also, if i waiting a few months, would the price come down a lot?

Note: System will run linux and all the hardware i have looked at is supported.

If they made intel core duo's at 3.2gig i would get one, but the fastest is at 2.67. Even though the core 2 duos and quad cores have lower clock speeds they are faster than the p4/d's etc.