There is a minimal performance gain in terms of the platform defaulting to dual channel mode instead of single channel mode. Except for benchmark programs, you won' t notice any meaningful difference. That said, dual channel is slightly better as it can prevent bottlenecks by providing two channels instead of one.
On a platform like yours, getting 1 GB modules is really a waste and I would rather go for a single 2GB or 4GB module that will allow me to add more memory if needed. Secondary, today's DDR3 memory is best bought in kits coming from the same batch and within the same series, else you are bound to get instability when mixing RAM later, even if its the same manufacturer and model number.