Sarah,
Keep in mind, the pre-flash sequence of your Canon camera will need to be accounted for correct use of your strobe of choice. The Bonica will trigger of the first slave pulse but your camera may not take the picture at the right moment based upon its sequence of preflashes.
The SeaLife you have a picture of listed is not the Digital Strobe (though you labeled it so and may have not foudn a picture of it at that time?). What you have shown there is the Analog strobe. The difference being is that the Digital version (look for it in black) has a power output setting (sorry scorpio_fish) on the back of it that you can dial in for more or less output. Both will work with your camera. scorpio_fish is correct whereas the analog version does not have access for power settings.
A better option for your camera and future use for other cameras beyond would be the Inon Strobes, particularly the D-2000 and D-2000S. Get the D-2000 if you would like a modeling light. These are probably above your expected price range right now but would be a more practical and complementary investment beyond thinking about today.
Lastly, similiar to that category would be the Ikelite DS51 strobe, but you will need the manual controller along with it for use with this camera. Though, I believe the Inon's would provide a much cleaner set up, more power and range, and the fiber optic option is very easy to use.
Good luck with your choices and don't be dissapointed in spending a little more in investing in something that has better range and one that will provide more enjoyment and less frustration for a longer time period.
