As a first time keyboard buyer I'm trying to decide between the Korg N5EX and the Alesis QS6.1. Whilst the Korg seems to have more sounds the Alesis has expandability. Does the quality of the sounds differ? Can the Korg be expanded? Does one connect to a Mac more easily than the other? Is one easier to learn than the other? Are there other features that diferentiate the two? Any help appreciated.