Question about transferring data from HFS+ to EXT4

Hi,

I have an interesting problem, in which I'd like to transfer all my data from a Mac OS Journalled drive (HFS+) to EXT4*. What would be the most efficient way to do this? I have a Macbook with USB3.0 ports, but which cannot natively read or write to EXT4. I also have a Raspberry Pi (only USB2.0, can read from HFS+). I've experimented with mounting the EXT4 drive as a Samba shared directory, but transferring all my media over wifi seems pretty slow.

*I'm trying to migrate my media library to a drive that a Pi running Samba can both read and write to, i.e. set up a NAS.

Any guidance muchly appreciated.