Garfish, Call Kevin Deal and see if he has a Line2SE left. I bet you can buy a new one and sell your Line2 for less than the upgrade cost.
I have a Line2SE with two Amperex 7308s , which I prefer to the Valvos it came with.
I have a Line2SE with two Amperex 7308s , which I prefer to the Valvos it came with.