Headphone amplifier - recommendations please

A friend has started doing online transcription work (via the computer) and isn't getting enough volume through her (good quality-Sony-32 ohm) headphones.

The problem is mostly because of the way people speak, with fluctuating sound levels and occasionally swallowing words.

Any suggestions for brands of headphone amps?

There seems be plenty on offer at AliBaba but it's hard to tell how good the stuff is, or whether it'll do the job at all.

Budget up to say, $NZ75

Thanks :-)

PS: An old regular amp might do the job, but it's kinda overkill...