I'd recommend swapping out the dimmer switch first. Slotts makes ones which are better than the stock ones. The stock ones have typically corroded to the point where the light output is a fraction of what it was new. Swapping my dimmer nearly doubled the output from the light bar.
If that's still not enough for you, you could probably swap the lights in the bar out for LEDs. Bars often come up for sale on ebay, moparts, or here for in the $50-$100 range.