i believe stockers are around 21-22lbs so performance will not be hurt a lot, but when you factor in grip from better tires i think it will be worth the tradeoff (BUT you can always get high performance tires for your stockers too).
if you are too worried about performance go for 17s and some really good performance tires. if you need more info try searching in the Wheel&Tire forum.

95 SE MTX DH UIM, 65mm TB, SC CAI, Quaife, Centerforce, Fidanza, UR Pulley, F/R Strut Braces, Cross Drilled Rotors, S.S. Brake Hoses, 18" Enkei RS5, SVT Engine Mounts+Inserts, MSDS & y-pipe, Trubendz resonated exhaust & MagnaFlow cat