need some help with choosing memory

hey

got a question

i am ordering my parts for a new pc

got a E6850
with GA-P35-DS3 mobo
evga GTX 8800 KO acs3
xfi prof
2x 500 gb WD re2 hd's
samsung 226CW
P182
corsair 620 HX
MX518 and G11


question is what are the best rams i can put in

it's a gaming machine so it needs to be fast
but not to expensive ..

so i was thinking 2x2 gb PC6400
or 4x1 gb PC 6400

does it make a difference?

What would be best timings i can put in - if it's 4x1 ?

please help

hehe ordering tonight

greetz

( didn't see this section when i first posted soz   )