Yes you can get sticks larger than 256 MB. You can see tested memory (untested doesn't mean it won't work) here:
http://www.intel.com/design/motherbd...nternalmem.htm
The motherboard specs say that the board hasn't been validated past 2.0 GB. You most likely won't need more than 1 GB anyway and for more than 2 GB you'd need a 2 GB stick (you only have 2 dimm slots) which is pretty damn expensive.