Batch EQ M4A data

Hello. With Toast and iTunes I have made a consolidated playlist. The playlist is in m4a format. With Toast I can normalize the files in one go and apply fades easily. This is all very cool but I am unable to find a utility (Mac or Windows) which EQUALIZE the frequencies of all these files at once. I want to cut away the high frequencies. I have an iPod Shuffle with the standard in-ear-headphones so I need to EQ these tracks. Ive tried Awave with DirectX plugins but the compression type is unknown (m4a). Ive tried Switch too but it crashes constantly.