HF-DC1 or 420EX or 550EX?

[ProAc_Fan]

Which flash unit is preferable to use on a G2? Or can I find a nice Sigma for even less money? There are so many flashes out there, how can I know which one will work automatically with my G2? The Canon HF-DC1 looks like a toy compared to the 420EX or the 550EX. Would the 420EZ also work with my G2 because I found a few of those very cheap at KEH.

I will be upgrading to a DSLR when funds and my wife permits it.

Thanks Mike