I have run with the PIAA Super White H4 100/80 bulbs before in Hella lens and they did work better than stock. BUT they are nothing compared to the HID setup I am currently using. READ: They H4 bulbs are no where close to HID.
The rewiring took about an hour to complete. Power draw is only 35 watts.The system I purchased is $200, so it is a little steep but WELL worth every penny.
http://www.shopxenon.com/vi_60.htm
I went with the 6000K model -white with a slight tint of blue.
...and with a 2 year warranty on the kit, it is a no brainer IMHO.
If you do stick with halogen bulbs PIAA makes the best bulbs and not all watt rating equal lumans on the road.