You can go 4.4 -> 4.3. However, you cant get the unrooted stock rom of 4.3, since Samsung/AT&T didn't ever release to the public (It was all OTA).
If you went 4.2->4.3 OTA, then your bootloader was upgraded. As you've seen on these forums, downgrading from 4.3 to 4.2/4.1 is a big no-no unless you want a brick.
4.2 ---(OTA UPGRADE)--> 4.3.
cyanogen 4.3-> cyanogen 4.4
cyanogen 4.4-> cyanogen 4.3
( ^ what I have done)
NOTE: After I got the OTA, I have never tried going back to stock. You can use rooted roms that are CLOSE to stock. But I wouldn't suggest going stock because of knox and blah blah blah.