I have a slightly different issue. I feel a lot less productive when reading on monitor (laptop or otherwise) compared to say a paper copy. At the same time the amount of content I go thru is fairly large (lots of preprints). I have tried iPad but ends up being distracting. Never found a comfortable path to opening pdfs on kindle. Atm considering giving remarkable tablets a try.

Remarkable is more geared toward handwritten notetaking. If you don't need such features and just want to read stuff, the high price is not worth it.

kobo-elipsa (and the all-new kindle scribe) have a similar large size (+stylus writing) at a somewhat lesser price.

Most kindles/kobos (and others too) support koreader [1]. this "app-mod" has a superb pdf reflow [2] mode that makes reading pdfs a good experience even on smaller displays (and these come with an even lesser price tag)

So koreader is the short answer. If you already have a kindle, give it a try. It is open source and easy to set up.

[1] https://github.com/koreader/koreader [2] pdf reflow is the pdf format equivalent to "responsive Web Design".