The Kindle DX needs - as fare as you can read all over the forum - a 1.8V USB-TTL-Adapter. All your links are 5V adapters, so you might destroy the serial port. However there was at least one person that was lucky with 5V adapters several times, but if you try it and you are unlucky, you trashed a nice Kindle DX. Personally, I was just in the same situation and spend $30 (including shipping) for a 1.8V USB-TTL adapter. It is 10 time as expansive but at the current price for Demo Units of the DX, I prefer to spend a little extra money and play it save.
TTL-232RG-VREG1V8-WE should (hopefully (is on the way to my place)) work.