I agree w/ DSDP_Don and I've been modifying headlamps in my cars for 20+ years. Back then, we had to go with non DOT approved "Euro Style" headlamps.
There are a lot of ways to make things better, and the prices are all over the map. Your choice in aftermarket headlamps could be limited. And, like others have said, you may be looking at beefing up the wiring anyway.
Its not just about brightness and wattage. Even coverage, for me, was just as important.
If there's room and a way - mounting some decent aftermarket driving and fog lamps on the front might give you the best bang for the buck. On my last Jeep, I did several things: upgraded the lenses (to Cibie), upgraded the lamps and then added some PIAA lamps under the bumper.