memory help please - new X2 build

i have a couple of questions-

i want to upgrade my memory to 2gb. i currently have 2x 512mb cosair & 2x 256mb ocz running on a asrock 939 dual sata with a x2 4200+ - the system runs dual channel @166mhz but not at 200mhz.

ive read i can only run 200mhz with 2 sticks, is this right?

should i be to bothered by cas 3 & cas 2 rating if im not overclocking?

should i try to match my corsair and all 4 slots ?

or should i buy 2x 1gb sticks?

if so Corsair Memory VS2GBKIT400C3 PC3200 2x1GB CAS3 @ £125 or

Corsair Memory TWINX2048 - 3200C2PT XMS3200 2x1GB 2x184DIMM CAS2 @ £198

thanks in advance

Welcome to the forums, Boon72!

Many of the A64 chips will not run 4 modules at DDR400 and most will not run un-matched modules in dual channel at all, so you're already ahead of the game!

Also, AMD systems get a bit of a boost from low-latency modules and if you're not overclocking, then the lower, the better for you.

To keep from losing a LOT of bandwidth, you'll need to use just two modules, else the command rate will default to 2T and it's a fairly big loss incurred.

I would suggest the TwinX2048-3500LL set, but they're hard to get right now and fairly expensive. For a bit less, the TwinX2048-3200C2's you listed are a definate good choice.

PLUR

CK