My local three store had a xperia z today (was very surprised at this actually) had over and hours play with it love everything about it and the audio is very good, it is more than loud enough. I also played with the nexus 4 again and the Z is louder not that the nexus 4 is low in volume.
Samsung Galaxy S5 Black 16gb
Previous owned Favourite phones:
HTC One X white 32gb
HTC One S Black 16gb
HTC Sensation XE Black
Samsung Galaxy S2 Black 16gb
Sony Ericsson Xperia ARC Silver