I'm deciding between the Kindle DX and the Pocketbook 903, myself. I have read on one of the threads here recently that the Kindle DX does not support notetaking for PDFs, and neither does the Pocketbook 903. I believe that note-taking for PDFs has been promised for both, in a future update (with the caveat that Kindle DX users have been waiting a long time for that update, thus far in vain, whereas the 903 is a very new device, so with any luck an update may be coming shortly). I don't own either device, so my information may be wrong.
Also, there IS a colour e-ink device, if you really want colour:
https://www.mobileread.com/forums/sho...=hanvon+colour
I think that it's priced at around $500 U.S.D (There is a link to the price somewhere in the thread), but I don't know where and how it can be bought.
Another choice is the iRex DR1000, if you manage to find it used somewhere (Craigslist, ebay). It's screen is actually somewhat larger than that of the KDX, and it supports mobipocket - so "liberated" Kindle books can be read on it, I assume. It has a touchscreen with note-taking capabilities. The problem here is that it is not sold anymore, and may be hard to find or expensive (I believe it used to sell for about $1000, if I recall correctly, which is why I never bought one!).
https://wiki.mobileread.com/wiki/IRex_Digital_Reader