Hi,
That all depends. You have to be careful with preamps as they can overload your scanner if you are near towers transmitting.
Is there a reason why you want to use a preamp? Also remember, that height is the antennas best friend and use good quality coax.
You did not mention which DPD antenna you are talking about. I can not tell you if it will be good or bad as everyone has different results with there antennas/systems. Don't be afraid to experiment.