The advantage of everclear is that you are not adding a bunch of water and diluting the flavor of your wine. If you are going to boost it with everclear everything has to be in balance, the acid and sweetness levels have to match the amount of everclear you are adding, if they dont balance each other out it will taste hot. We use everclear in our dessert wines to give them a little boost or add just enough to balance out the sugar and acid levels. Good luck, blackberry port is great.
Crackedcork