If you install 2 x 8GB RAM modules or even 1 x 8 GB module it will not affect your warranty. This is the spec page for that RAM on the Samsung web site. Newegg has those modules in stock here. As for the best upgrade method, it has always been to replace the RAM as a kit for matched compatible RAM. Crucial has that RAM here. Crucial RAM has always been the most compatible with Dell systems.
Just purchased a Inspiron 3891 with 8MB RAM, thought that I may want to increase the RAM to 16MB so I checked the part number and guess what? Nobody at Dell can idetify it and Samsung say its not listed, so how on earth did it get in a new machine??  Any ideas anybody what I can do about getting another "Samsung M378A1G44BB0-CWE 8GB" or do I have to get complelty new RAM sticks and if I was to, how will that effect the Dell guarntee???  On a side, I have bought 3 Inspirons over the last couple of months and a Dell screen from Dell France and it has been a nightmare dealing with Dell France, big mistake on my part - so, be warned when dealing with Dell France. (Dell US and UK, no problem at all) [IMAGE]Samsung M378A1G44BB0-CWE 8GB
Samsung M378A1G44BB0-CWE 8GB RAM