It definitely looses the warranty, but if you remove the strip from the speaker, it will be far more louder.
The Xperia is a good device, just you cannot do one thing with it, call from a train. (i have seen iphones working smoothly even if the sorrunding was quite noisy, with my phone i was not able to hear just in a very decent environment.) Now it's better. 
Unfortunately previously i had problems with the microphone, and the fact is, it can be dirty and you need a pin to clean it up.
