Roy, I think you and your wife both deserve something special for paying off 15k worth of debt, she gets the new kitchen makeover and you get the DX
You've spent so much time circling the Kindle, examining the purchase from all angles. It's not just a quickie impulse buy but a well thought out purchase of an item you'll use for years to come.
At this point if you can afford the DX then you should get it.