HID's inserted into a housing for a halogen bulb are illegal in most if not all states, the light gets scattered and instead of making a beam that illuminates the road you get this glare producing mass of light that blinds oncoming drivers / riders.
I am highly oppsed to HID's unless a. your lens housing is designed of it as to reduce glare. b. you have a mode for low beam halogen then when you switch to high beam you get hid output, this way you can run those HID's in the middle of nowhere but can switch when you see a car coming.
Unfortunately the charging system on the 750 is insufficent, I have put a 80/100W bulb on my vn800, with a relay driving the highbeam power (with a thicker wire for less voltage drop) and it is plenty bright. 80/100 is also illegal but it does not scatter light all over the universe the way an hid will.
As WM said, aiming is very important in getting the light to produce light in the right area.
Also if you want more light and is totally legal, you can run a ticker wire to a relay then the relay to the bulb for high or low beam (I suggest high beam), the reason for the thicker wire will be to reduce voltage drop in the wire, light output is reduced substantially, I think almost parabolically with voltage level.
2000 Vulcan Drifter 800
Roadhouse classic 2 > 1 exhaust
Okie Smokie intake config
52K miles or so, always going up
Painted flat black winter '12