Apple uses the same Realtek chipsets anybody else does, and I doubt that the implementation is any better.
They work fine as a DAC, but are strictly current limited and suffer from high output impedances. If that is an issue or not depends on the headphones, the Sennheiser HD 5X8/5X9 are easy enough to drive, but a high output impedance source results in a serious inflation of the upper bass, when they are rather bassy to begin with. He could correct that via EQ of course, or get something like a Meizu HiFi Pro dongle for around 25§ or so, that will work beautifully with any reasonable common headphone (1.8Vrms is fine for almost all of them really, just not something like the 600 Ohm Beyers).
The Apple dongle is somewhat limited in output level, but could be a good alternative either as a DAC fed into an active load or for easy to drive headphones (like the Sennheisers mentioned, they will work fine off of 1Vrms). Similarly to the Sennheiser offerings, the Philipx X2/HR could be an option. Behaves about the same as the HD5X8/5X9, if it can be had cheap at the time (fluctuates, I'd not spend too much money on it since it's not repairable with no parts available, not even original replacement ear pads), look for around 120$/€ or so, same price as the HD 599.
Point is: if he is on a limited budget, there is really no good reason to spend a lot of money on a DAC/amp combo. Just get some headphones that work without it.
