All this matching stuff I think is irrelevant.
If your mixer has the IF port, 50 Ohms, specified for DC to several MHz at least, then the audio frequency spectrum is so narrow that any mismatch cannot affect it. If you want to be sure, use simply a series resistor ~20 Ohms, to match your 32 Ohms to 50 Ohms. Make sure there is no DC component from your audio source (use a 1 uF -10 uF capacitor to block it).
If you do not trust me, take conversion loss data for all suggested matching devices. You will see that none matters except of adding some loss to the IF line.