DC's
Try looking at some other headsets.
Sennheisers are good and there is the new beyer dynamic.
I have always found the 13.4 a little flimsy and not very good passive attenuation in light aircraft.
Even in commercial aircraft, they are not very good.
Just my opinion. Its just people recommend them without a true comparison through usage.
Pooleys do an ANR headset with a connection for MP3 and mobile phone for
c.£220. It's based in the Pilot model and won an award i think.