Precision's AirForce can control the factory down air bags or if you do not have down bags already you can add down bags from Precision Planting $170/row or if your system uses springs some times you can add just the lift bags to the current spring down force system.  if you want to do lift you will need a new bracket and lift bag from Precision Planting $170/row.  to add completely new down and lift bags and brackets its $250/row.  all systems except existing will need some air line kits also.  

one thing to remember is that the lift system will give you a faster reaction time than down only.  The lift bags are about 1/4 the size of the down airbag and it takes less air to make a adjustment.