Simple question, complicated answer. A device needs to swing voltage and current and when a vendor only publishes voltage you have no idea how well it supports low impedance headphones without more detail. 4V is meaningful if your headphone is 150 ohms or up as if a device can swing that voltage it needn't put out much current so it's probably it delivers its full power based just on voltage.
In theory 4V RMS = ~1.3W into the AEON, IF it doesn't current limit. If they publish detailed power specs where power doubles when load is cut by half you'd likely see this... 1W at 16 ohms, 500mW at 32 ohms, 250 at 64 ohms. If the amp is running out of current, the number at 16 won't double the output at 32, it may be the same, or even fall, for example 500mW at 16 ohms.
If you don't crank it (and spare your ears) it's probable 4V is enough, but some people like it LOUD, and for that you need more specs or to reference a model Amir has mentioned to check power.