the older Kindle touch has twice the capacity of the newer PW ( 4Gb vs 2Gb) according to the table I linked to earlier, so it should hold over 3000 "normal" books ( or about 30 if your books are like anothercat's

) . The OP already has 1,395 books so a 2Gb PW will have little room to spare for more new books.
so Kindle touch could be a better + cheaper choice, unless the lit screen is essential