Decent handling susp setup?
Moving the battery is the last thing I would worry about. Tire choice, torsion bar and spring rates, shocks, sway bars etc make a MUCH bigger difference. Especially if you're running a newer style battery to begin with. Moving 30 lbs on a 3500 pound car is a pretty minor effect. I'm not saying it's not worth doing, but it would be pretty low on my list of priorities. For the record the battery on my duster is relocated to the trunk, but that had a lot more to do with it being in the way of the J bars I installed.