Heavy duty relays and very good grounds might solve your dim light problems without going to the super bright headlight bulbs. The dimmer switch in particular is a source of resistance that can dim the lights noticeably, particularly if you're still using the original equipment floor-mounted one. Check the actual voltage at the headlight bulbs, compared to battery terminal voltage, then find the source of the voltage drop if the lights are getting noticeably less than charging system voltage.
Jerry
