Does it have to be new? A gently used IREX would be worth considering in that price range. Not the latest & greatest, but solid, big, and probably reasonably had on e-bay (I have no idea what a DR 1000 would go for, but that or the 800 should work for price & check all your boxes).
I still occasionally use my old Iliad when I want to read pdfs, and don't find it too slow at page refreshes. The 10" screen of the DR 1000 would be just about perfect, and the speed of either the DR 800 or 1000 would be better.