yup, K790i does take more than 2Gb cards. However in SE site, it says upto 2Gb,,,maybe coz only upto 2Gb was relased when the page was upped.
ive heard in Se NSE, some are using sandisk 8GB cards w/o ny probs.
but the oldest firmware only supports 2GB, but updating it via PC or phone itself solves it easily.