For side buttons, SD Card, and epub support the cheapest option by a lot is NOOK STR.
Beyond that the options move to specific models of the second tier, hardware-only vendors: Pocketbook, Onyx, Bookeen. They're not cheap by current standards.
The walled garden readers have really decimated the field.
Without SD, the Kindle4B is the most affordable and it has excellent rigidity, which I remember is something early Sony users value.
Without the side buttons and *with* SD Kobo pops up.
I'd second the suggestion to wait and see if Sony does a T3 and rethinks the decision process that led to the T2. Might the 505 last 6 more months?