Amazon might be announcing a tablet next week, see
Amazon press conference, Sep 28. B&N may also be refreshing its tablet (and/or introducing a new one), see
New Nook news Sept 2011. So I suggest waiting a week or so. Most of the rumors suggest both are going to still be $250 for a 7" tablet, but price is typically one of the most closely held pieces of information before a device is introduced.