seriously facepalm.
ask him do the math.
very loud if compared to HTC One M8. but bear that notifications volume will be lower.

I like this phone very much.
Almost 1month old, and never face a single lag yet. But i am a very light user, didn't play games, just browsing, messengers... still have 1gb free ram.

So far, it is a very good experience with the phone.

even though Note 4 is louder, but sorry to say it is not enjoyable because it is not stereo speakers. Z3 has dual front facing stereo speakers, and the back facing mono speakers (Note 4) produces flat sound.

and i can say this phone never lags because the system is very light.

I had used Xperia Z n XZU ( 3g n LTE) n my only complain is its very weak phone speakers ( due to extra membrane on speakers for waterproofing). Had several bad experiences missing call in noisy environment. I discouraged those to buy if they wish to use as media entertaintment unless they don't mind using a headset or earphone with it.

Stamina mode helps you to get to 2.5, 3 or some people reported even 3.5 days usage in 1 charge.

Unless you a heavy gamer, you should get at least 2 days per charge. I get an average around 2.5 days, sometimes 3 per charge