Dimarzio makes atleast three split coil Jazz pickups, you may want to consider all three.
They all will be slightly hotter output than the stock Geddy Lee's but they all will give you different tone.
These three are:
Model J
Ultra J
Area J
The Model J's are supposed to be the least traditional "Jazz sound" of the three, some complain they are too boomy. The Area J's are supposed to sound the most like traditional J pickups, with the Ultra J in the middle. The Ultra J's certainly have a hotter output than what you have now, and will sound a bit more modern, the only reason I am weary of suggesting these to you is because many people complain that they are too "scooped" and you specifically asked for a pickup with "hard hitting mids".
Check out Dimarzio's website for some comparisons of the three as well as search around the forums for comparisons, and shootouts.