He explained (in simple enough terms) about ram, and getting matched ram chips.
Right. Most machines run fastest (with current applications) with four 256MB DIMMs or two 512s.
Two 1024MB sticks or four 512's usually make the machine run somewhat more slowly due to the extra CPU cycles that are needed to maintain communication to the extra banks and the RAM real estate they contain.
I have built several high-end gaming rigs where the client demanded, against my advice, to install two or three GB of DDR.
And, without exception, those machines ran slower than mine did.
As I have said, the only rigs that need more than 1024MB of RAM right now are those that will do mostly video editing/encoding duties.
Good luck with your shopping!