Depends on the planar. Use the math to calculate the Current and Voltage required to drive, let's say, MrSpeakers ETHER Flow (96dB SPL/mw @1kHz, 23 Ohms). You'll see that it won't need anywhere what the DAVE is capable of to reach 120dB peaks. The ETHER Flow requires just 2.4V and 104.35mA, 250.43mW of power to reach 120dB peaks (again, VERY painfully loud). The dynamic driver Utopia is slightly different in the impedance curve because at 50kHz the impedance rises to over 300 Ohms so it will require more Voltage than the 80 Ohm @1 kHz impedance spec implies. However, this is also not an issue for the DAVE's output though (the DAVE's 500mA is quite a bit of Current for most planar headphones). The speaker world knows these calculations VERY well and a user can calculate the power needed for the transducer taking in to account distance as well (headphones really don't require the distance SPL falloff calculation). On Head-Fi it's just myths and unicorns regarding power and generalizations, and it seems some users can't distinguish total design / tuning / synergy from output power. I listen to the ETHER Flow (a planar headphone) at around -30 to -40 on the DAVE volume depending on the genre and track. So you are trying to tell me I need even more headroom because the output isn't enough. I don't think so.