I have got the standard 30W in both the dooms in my Fazer. The mechanic suggested to go for the battery used in Yamaha R15. The standard wiring for Fazer was retained. I have been riding for the past 5 months with both the dooms lit in low beam with no issue.

Putting up two bi-xenon lamps simultaneously is quite next to impossible without severe modification in the elctricals of your bike.

A single xenon HID consumes around 8 Amp while starting and reduces its consumption to 3 Amps when fully lit. So even for a single Xenon set up our stock battery of 5 Ah is not sufficient to provide that much of power.

For that you would have to rewind your stator coil with 19 gauge wire , Change the RR unit with that of Piaggio Ape or GC 1000 and replace your batter with minimum 9 Ah capacity.

If you want to avoid all these hassles with some compromise then night breaker or xtreme power will be a better option.

For a 60/55 watt lamp ... 55 watt is for high beam and 60 Watt is for low beam combined it with the tail light of 5 watt .
So high beam + tail light = 60Watt can be easily provided by our stock battery.

And for occasional honking say for 2 -3 seconds would consume around 30 watts which is also bearable by our battery.

Remember our magneto has an capacity of around 80-100 watts so it can very well assist our battery during heavy loads but not for long.

So a single lamp of 60/55 is a very good set up.
Don't forget to adjust the beam setting after installing the lamp.

At least I am happy with the throw of the light on the highways.

Any further query will be highly entertained.

What are you talking about extensive modifications? The initial current draw is for a few seconds and that doesn't drain the battery to death. Please do NOT exaggerate. Its possible to run 2 HIDs at the same time. A lot of fazers here in my city have dual HID bixenons and they also run flawlessly on my friend's fazer. Earlier we connected the two halogens to work together. Then we tried HIds and trust me it works!