I have the Stealth and an ADI-2 DAC. For me, it is sufficient. Only when listening to very quiet classical recordings i reach the 0dB point of the ADI-2. I almost never do this though.
If you want to listen to quiet or high dynamic range records, you could face the limits of the ADI-2 sometimes. So, if you want to test which one is better, don't bother with "sound quality " differences, because there should not be any, but concentrate on your most quiet recordings and see if the ADI-2 gets loud enough for you with the E3. If it does, you probably don't need the 2/4.
If you want to listen to quiet or high dynamic range records, you could face the limits of the ADI-2 sometimes. So, if you want to test which one is better, don't bother with "sound quality " differences, because there should not be any, but concentrate on your most quiet recordings and see if the ADI-2 gets loud enough for you with the E3. If it does, you probably don't need the 2/4.