E7. Don't bother with the other Fiios for low ohm cans. The E5 also has bass roll off as if it were high ohm, so nix that too. Grado clone might work, but still no word on whether it's got a rail splitter or what impedance it is. Also don't know if the battery blowing out cans would still be a problem like other cmoys. E7 is a safe bet.
Lol, E7 for the T50rp. Very funny.