well i can tell ya and tex that the sirio has a lot more power then the 2.5. We both ran a total of like 3 sirio's back in the maxx day. It was a huge improvement over the 2.5. Actually towshen has my last sirio that i sold him and he noticed on the first tank about how much more power it has. Give it about a half gallon before it will start to wake up. Around a gallon its just gonna all the sudden giving you power outa know were.