While not "new" in the modern sense, modified ROMs (originally for K1 boxes) have been refined to work on S805 hardware, providing slightly better app compatibility than KitKat.
To find a new firmware for your Amlogic S805 device, you can try the following sources: amlogic s805 firmware new
Armbian provides a modern Debian/Ubuntu user space for the S805. While not "new" in the modern sense, modified