Buying an SLR can be simple or complicated.
If you want 'the best', the answer is the Canon 1DsMIII - but it will over-complicate matters, and will probably make shooting a hell of a lot harder.
Compacts these days sport a lot of things that dSLRs don't - they auto adjust colour, exposure, saturation and sharpness to 'optimums', so the snaps you take always come out looking vibrant and happy.
The essence of a DSLR is control and choice, so they won't do the above things by default. You'll have control over every aspet of your photograph, whether that's a good or a bad thing. Shooting on a DSLR versus a compact means you lose, at least initially, the simplicity of flicking between macro, wide angle and zoom. Want to shoot macro? that'll be 1k, 2+ for a decent - same for wide and tele - and more, especially if you're throwing L [or equiv] glass on.
There's also the lug factor, as well.
It comes down, generally, to lens and body choice - Canon or Nikon.
Canon have a great range of dSLRs, with the focal length crop, but digital lenses to compensate, or full frame, such as the 5D.
The difference between the 5D and 1D[s] series is body, build, and flash sync, essentially.
I can't speak for Canon gear, as I don't shoot on Canon.
Work out what you want and need to do on your camera, and then see which one fits, not the other way around - then stop over at dpreview.com
