If you are upgrading your headlight hardware and are trying to do it on the cheap... STOP NOW!
If you think your headlights are not adequate then the first thing you should do is a rewire...
http://www.danielsternlighting.com/tech/relays/relays.html
If your headlights still are not adequate then the only option you should consider is the Hella ECode headlight and a QUALITY H4 bulb - do not just pick up some cheap-o bulb that touts anything relating to "Super", "Hyper", "Extreme".
IF these two did not satisfy your need to upgrade your headlights then... and only then... should you consider the VERY expensive option of completely reworking your headlights.
IF you consider this path at no time should you even think about using an "Auxiliary" light in place of a headlight. These lights were not designed to be a main beam and are not only illegal but also dangerous to oncoming drivers.
Going this route will involve pretty substantial customizations to get right - read "not just throwing some stuff together". This is a safety element of the car. Don't mess with it lightly.