A lot depends on where you ride, and how fast you want to go.
In the past I used the EL320.
It's not very bright, more of a 'be seen' light, good battery life, unless one of the four AA batteries gets weak, then it gets very dim.
For a single 'torch', look at the Fenix L2D or LD20, you can use it as a flashlight also.
The magicshine MJ808 is better, brighter, and can last much longer on a charge.
In the middle of winter, I use the MJ808 on low, charge it one a week, and L2Ds as backup/boost lights on the bars... more lights on the helmet (to each his own).
I would start with a good light for your needs and budget, and add more if needed.