I plan on fitting H9 55w 4300K HID's to the high beam & H7 35w 4300K HID's to the fog lights in my Series 1 VE SV6 and leave the low beam standard halogen as this avoids attracting attention from the fuzz and HID light scatter from the low beam due to having reflector lenses which is annoying to oncomming traffic.
I had a full HID bi-xenon High/Low + High beam conversion on my VT i recently sold and even though i lowered the low beam focus on several occasions it got to a point that it was pointless having them.
Oncomming traffic still used to flash me sometimes and i know i dont appreciate it when other cars comming towards me have low beam HID's that are incorrectly focused or being used in reflector headlamps either.
This way you have the best of both worlds, Super bright on high beam whilst still being user friendly to other people on the road around town and when passing on the open road.
I travel 150kms return daily for work leaving in the dark with the odd kangaroo to be weary of so ultra bright high beam is a must and to be honest i am a little dissapointed in the VE's standard headlights.
They guy i car pool with has a VZ wagon with standard halogen headlights and they are miles better than the VE, holden definately went backwards with the VE's headlight quality. Well the series 1 anyway, i am not sure if the series 2 is any better.
The H7 rallye+65 (Osram only):65w @ 2100 lumens @ 500 hours, do seem the obvious choice for low beam as far as lumen output and durability so i might throw a set of them in to help things on low beam.
Just remember that having non OEM HID's fitted could have serious insurance implications but for my situation i think its worth the risk so long as you take the time to make sure they are set up correctly