Best 1GB single stick for a MSI mobo s754 @ AMD 64 3400+??

Whichever has the lowest timings at the best price.

That was easy...

Well, they all cost the same and all are CAS 3, except for G.Skill which is CAS 2.5. Thing is, my mobo only has two rows for installing memory - it already has a Samsung 512MB pc3200 @400MHz CAS 3...so, will mixing and matching work, cause I don't feel like buying the wrong stick and all the hassle it brings.

I just want to get this thing over, my PC is too slugish and I've been putting off this purchase for far too long.

I'm not sure if this link will work
http://www.newegg.com/Product/ProductCompare.asp?Compar...

Ah, one more thing...how does DDR work -
do 2x 512MB (same brand) on two slots make it double rate??
and does 1GB in one slot make it single rate :?: ??

As I mentioned, I have on stick of 512MB installed, but apart of not knowing which brand will work on my mobo, I don't know how to best configure it...meaning, will 2x 512MB same brand on two slots be more effective than e.g. 1GB stick in one slot only - if trying for a total 1GB memory configuration...confused indeed :? .

Don't confuse DDR with Dual Channel. Socket 754 doesn't support Dual Channel so disregard that. All current AMD processors, from the original Athlons to the present do support DDR. In single channel mode, any RAM you put in will run at the speed of the slowest memory you have installed. Matching isn't necessary.

The G.Skill would be my choice for your setup. Lower timings, should give better performance.