Choosing the right High Put Alternator

I have a 2002Chevrolet Surburban LT & i've been doing work not only the matainance of my truck but installing the system. Im running 2 DVC 15' Kicker CompVrs in a sealed box that are 2ohms on a hifonics brutus bxi2006 2000watt super class d mono amp. I wired them parallel & in series down 2 1ohm also tried jus parallel @ 2ohm & both ways when i raise the volume @ a certain point the amp shuts down. I read its because I need a high output Alternator. I do have a yellow top optima battery but my alternator is only 105. What amp output would b best to run this system. I also do plan on adding a 4 channel to push my 4 kickers door speakers as well eventually.