Does it really matter? it reminds me of Keeping up Appearances where Mrs Bucket tells everyone her name is pronounced same as "Bouquet", I also used to know a guy whose surname was "Onion" who got infuriated and told every one that it was pronounced "O-ny-on".
At the end of the day there is no right or wrong, Asus may prefer "Ay-suss" (which sounds daft to me) but people will call them whatever sounds right to them and for me there is no 'y' in Asus and only one 's' on the end.