If you are going to purchase now and your budget is somewhat limited you might want to consider AMD CPU's.
At this juncture AMD CPU's are faster for gaming, though that is about to change.
AMD CPU's overclock readily and can give you a free "upgrade"
Yes Conroe will be costly:
In addition you might want to take a poll or do some reading on the dual core issue w/ gaming. The majority of games are not designed for dual core - yet...
I am a gamer w/ a dual core and I have been able to work the bugs out - wasn't too difficult.
RAM - Definatley 2GB
HDD - Maybe a larger capacity (won't cost too much more).
OC'ing? - Maybe a Zalman or Thermaltake
Vid Card - Try the 7900 GT KO - good price w/ headroom to OC