I'd recommend the Nexus 7; I'm really happy with mine and love the quad-core processor which speeds up everything you do.
After a bad experience with the slow-as-molasses Kobo Vox, and their abysmal customer support I'd be reluctant to Ever have another Kobo device (although their e-reader software is OK)
So just order the Nexus from Google's Playstore - it arrives quickly and sets up easily and synchs right away with Google-everything that you have.
(You seem to have already eliminated the RIM PlayBook, which is too bad - because if you're looking for a good deal, they've just been reduced to $150 here! Excellent devices originally designed to sell for about triple that price!)