Sam,

The mounts on the Olympus and the Canon are different and your EOS lens will not fit the Olympus. I would personally lean toward Canon, because you already have glass that will work on the EOS Digital cameras. If you really want to replace everything you could also look at Nikon, both Canon and Nikon have great systems with a lot of lens and accessory options. I personally shoot with a Canon 1D MKII at this moment, but have shot with a 20d and a 10d in the past. I would steer away from Olympus DSLR system just because they don

i disagree with Mike on the Oly line up of lenses and accessories; for portrait and wedding purposes, the 28-108mm (equiv)lens can be left on the camera and maybe never come off. Actually, the 28-400mm range can be covered with just 2 lenses,all 2.8 glass, btw, add a WA if you are into landscapes. I use my old Seligman bracket with the FL50 flash and a remote cord to attach it to the camera.
This set up covers groups, individuals and shots from the balcony of the church quite readily.
The auto sensor cleaning and pixel mapping features are exclusive to Oly, something to consider. According to NYIP, the ccd sensor needs less post processing than the cmos that Canon uses.
Whatever your decision, don't try to go too cheap. Some low end flash units don't even have manual control!