Headsix is the best choice in these three.
My SuperFreQ would still hiss a little on Mini3 but got no hissing at all with Headsix.
Yet, Mini3 is still better than iPods headphone out-put.
Mind me, Mini3 has a very good SNR rate, which is about -105 ~ -108dB, while the iPod is only -90~-96 dB at best.
As for the headsix...... well, it's SNR rate exceeded my recording equipment's ability which is only -108dB. So it must be lower than -108dB to be presenting no hissing with SuperFreQ (Since -108dB's Mini3 would still hiss a little.)