kindle as a second monitor question

hi
i read an article on the net about using kindle dx graphite as a second monitor and want to buy kindle dx graphite with 2.5.5
to use it as a second monitor because my eyes can't stand pc screen. but so far the one i found for sale
has later, updated version of OS ( anyway its original OS ver. was 2.8). Does anybody know is there a source where i can download ver 2.5.5?

also nowadays are there any other ways to use anything with e ink as a second monitor?