if you cant do both, do the pre-amp first. The preamp will do more justice with the old pickups. New pickups wouldnt benefit much with the old pre. Also like mjl422 suggested, I'd go with the 3 band over the 2. you get more versatility. if you dont have enough holes for the knobs you can either get stacked controls or have a skilled guy drill a hole (stacked controls is simpler and less hassle).
yeah, i hate the passive EMGs and the high end ones are active, which dont work with every pre config, so its best to go with an EMG pre, which ends up being a 2 for one shot, which is probably more money than u wish to spend.
but a pre will cost less than a set of pickups, and have more effect than the pickups if changed alone, so the new pre is probably the way to go.