Solution
I have to admit, and particularly in reference to Intel machines, I have has extraordinary luck with RAM choice. I have mixed manufacturer, speed, timings and rarely had any issue with any of it not working. Of course it will default down to your slowest timings. I have (almost) never had issue mixing RAM with the same size, speed, and timings.
My consideration about this particular situation is to go with whatever cheapest option might work to increase your RAM. That should buy a little time so far as use, but overall I would think at that age replacement of the system might be a consideration on the near horizon.

punkncat

Polypheme
Ambassador
I have to admit, and particularly in reference to Intel machines, I have has extraordinary luck with RAM choice. I have mixed manufacturer, speed, timings and rarely had any issue with any of it not working. Of course it will default down to your slowest timings. I have (almost) never had issue mixing RAM with the same size, speed, and timings.
My consideration about this particular situation is to go with whatever cheapest option might work to increase your RAM. That should buy a little time so far as use, but overall I would think at that age replacement of the system might be a consideration on the near horizon.
 
Solution