best ram for 4gb overclocking

[Chronictank]

Hi,
I currently have :
GeIL 2GB (2x1GB) PC6400 800MHz Ultra Low Latency DDR2 Dual Channel Kit (GX22GB6400UDC) (MY-058-GL)
Which can be relegated to my brothers pc as i found it isnt the best clocking ram in the world but gets my E6600 to 3.2Ghz on 2.2v

First question:
i have been reading about and i cant seem to get a definative answer, i dont really want to spend over £260 but is it better to get
2x2gb ram or is it better to use 4x1Gb?
4x1gb seems cheaper but is it really worth it? or is there a reason to go for 2x2gb?

My second question is whether to buy PC2-8500+ memory instead of 6400, as i seem to have reached the limit of my memory at 3.2Ghz

And finally bearing in mind the points above what memory do you recommend i get?
I was looking at:
http://www.overclockers.co.uk/showproduct.php?prodid=MY-068-GL&groupid=701&catid=8&subcat=817
for 4 matched pairs

Thanks in advance

 

[ergonomics]

do you really need 4gb anyway? if you're worried about cost just save some of the money i guess.

but i guess the 2x2gb will alloow more in the future, if required

edit: also having 2 sticks instead of 4 seems to mean that the chipset has less 'work to do' so can lead to better overclocks (in most cases i think)

 

[Chronictank]

i'm not worried about money really, just setting a limit so i dont go overboard.
I need 4gb as i run vista ultimate, and the ammount of disk activity (had 4gb previously) between 2 and 4 is noticable