Whatever memory you have will work at the speed of the slowest module. The companies do not matter, except on some newer ASUS motherboards and ASUS laptops.
Enter your computer brand and model, into a search at
www.crucial.com, where you will get a trustworthy report of what memory modules your system can handle.
If a faster module will work reliably, Crucial will list it.
DDR200 is PC1600
DDR266 is PC2100
DDR333 is PC2700
DDR370 is PC3000
There may be others I have forgotten.
Generally the brand changes do not matter much, though some memory is made poorly from bins of chips, and that is called "third tier" memory. It is not tested before it is sold, although it may have a warranty. You become the tester. When it fails, they give you more.
All of the above are interchangeable in most DDR machines... if they are all the same, and not mixed with some PC2700 and some PC2100 or whatever. But the only way to know is to try, and that gets expensive. Since you are using PC2700 memory, use that or faster, but try to have all modules be the same speed. Sell your existing memory, and buy the larger modules.
However, if Crucial says it fits your brand and model, it fits, except in ASUS motherboards... regardless of the memory brand.
AVOID Value RAM, as it has slower timings and latency.
You will not go wrong with Crucial, Corsair, Kingston, Infineon, Samsung, or the memory you were recommended, Apacer or Avant.
