I'm not sure of the current rating of the wiring but I wouldn't risk it. The upgrade you are suggesting is almost doubling the load. Try the 'extra' bright bulbs from Halfords or similar. They will not cure the problem but it will improve it slightly. Many people have said on here that it is not infact the brightness of the bulbs that is the problem but the refectors in the headlights themselves being of poor design.
Using high wattage bulbs in modern car headlights can cause the reflector to deform as they are now made of plastic http://www.ltregister.f9.co.uk/graphics/sad1.gif border|EQU| 0 align|EQU| absmiddle > It's a requirement for modern cars to have reflectors that adjust the height of the dipped beam aim (doesn't apply to main). The light manufacturers are using a plastic reflector that moves within the light unit to meet these regulations.
If your car has this feature you will do more harm than good fitting the higher wattage bulbs.
I've used 80/100W bulbs in previous cars without any mods, but make sure that the dipped beam runs through a relay first (don't want to over-load the light switch)
Go along with Hornets (Heave Ho 6) suggestion and get some brighter bulbs - you'd be surprised by the difference between different manufacturers 55/60W bulbs for actual lux [img]http://www.ltregister.f9.co.uk/graphics/happy1.gif border|EQU| 0 align|EQU| absmiddle >.
Changing headlamp bulbs to a higher wattage than the manufacturer uses is Illegal.I know lots of people do it but if someone crashes into your car and claims they were blinded by the lights you will lose your insurance and could be prosecuted if the bulbs are found to be brighter than they should.A mate of mine has a 306 with a twin headlamp conversion and his lights are stupidly bright,I am suprised he has not caused an accident yet.
Auto Express has recently tested all the different bulbs. By far the best were Philips, who do a '50% brighter' xenon 60/55w, at about £20. Also recommended were the Halfords '30% brighter' xenon, at less than a tenner. IIRC, one of the worst on test were the PIAA bulbs, which were also the most expensive!