5 5 5 15 is very common, I would stick to this and buy used for a cheap price.
I have not come across problems mixing corsair, kingston or several other brands at these timings.(tho 1.9 volts setting was a must)
The latter set is obviously inferior lower grade ram. mixing kits on old machines is all guesswork and luck (dont spend big bucks, it might not work anyway).
Thanks a lot for the answer Tea Urchin. Is the latency the only thing that's lower grade about it or is there some other aspect? Cos it seems such a subtle difference to my novice eyes.
But I'll probably hold out for some used RAM that matches 5-5-5-15 anyway.
Unfortunatley the only used stuff I've seen on Ebay so far seems almost what you'd payfor new RAM now. I dont understand that for such old RAM.