best suggestion i have is to cut the ground wires at each bulb connector and run a new one. then go to the harness at the left side where the dash harness comes through the fire wall. cut the low and high beam wires. you then would use those as signal wires for relays. this takes the load off of the switch and boosts the juice to the bulbs. it's a huge help in it's own. while you are at it you could even set it up for qaud beam. same as above but you would add a third relay that would fire from the high beam wire to the low beam aswell. it's a simple set up that is very effective. you retain all functionality and there is the added bonus of if you decide later to do bixenon bulbs or bixenon projectors your harness is set up for it already!
i used 25 amp breakers (not fuses. fuses work fine just a personal thing) with the normal 30 amp relays.
the basics are solder all the connections and heat shrink them.
use dielectric grease on all connectors (relays and fuses/breakers)
use wire loom to dress it up.
for a cleaner look head to a junk yard and find an old nissan. they had a bank of four relays in a nice little box that is great for this. makes for a nicer install. when you finish this the wires would be
pin 85 for ground on all relays
pin 30 for battery power (fuse this ckt)
pin 86 is where the wires for high and low from the switch would connect.
pin 87 is for the lights themselves.
for quad beam your low beams would have one relay connected to the low beam wire.
then the lows have a second that is turned on by the high beam wire.
then the highs have one turned on by the high beam wire.
the purpose of two relays connected to the high beam is to isolate the two ckts so that you have seperate high and low beams.
now this can be done with 2 relays and the high triggering both and a diode to keep the low beam from turning on the high beam. but this set up is also easily disabled to go back to normal lights. either way will fix your problem and help out with overall output. i suggest the relays though.
oh and also the relays would give you the option to add fog lights for lowbeam supplement that could easily be set up to switch off when going to high beams if you don't have them from the factory.
one last piece of advice is when you hook up the output (pin 87 to power bulbs) cut the wire at the left light in two then solder the three together. then the ckt doesn't have to be overylayed with bigger wire since the load is cut in half for the part of it from the switch.