H11 to H9 conversion is probably going to be the cheapest mod for more light output for low beam on the quads.
Trim the top tab:
Trim out the piece out of the socket:
That and you can do a 9005 to 9011 conversion for the high beams as well. You would have to trim the top tab of the bulb like you would with the H9 conversion.
The other option is the LEDs as others have said. I was looking at LEDs but decided to go HID/LED conversion. Look at GTR Lighting Gen3's, Morimoto 2Stroke 2.0's, Supernova V4, even the Phillips have a good output in LED bulb offerings. The Hikari Ultras have gotten good reviews by members here.
Not promoting any particular brand, just what some of the reviews I have seen indicating an increase in output and that have good cutoffs and hotspots. Not scattered light and poor light performance.