Thanks a lot, Spinfex. I will get a 32GB SDHC and test if it is readable from DreamPlug. I didn't know that there is an SDXC which can be up to 2TB. I haven't seen it sold anywhere.
Part of the spec for SDXC is that the file-system has to be xfat(?), which is a proprietary Microsoft file-system. There are, I believe, some digital camera that support it.