Laptops are more picky about their memory than desktops. I would stick with 2700 just to be safe.
I would just add a 1 GB stick. The second memory slot is a little difficlt to access, and it would also allow you to drop in another 1 GB stick later on if you want. Cheaper and easier that way. It's not dual channel so there's no need to have matching sticks.
I bought mine with 256, and then dropped 1 GB into the free slot when I got it.