While I use DSLR's on the surface, one thing to consider is that a DSLR housing often costs more than the body itself, before needing other parts like ports for your lenses and focusing gears. For this reason, I shoot with a compact underwater.
IME some of the best DSLR housings are made by Nauticam. That housing, for your camera, runs about $3300 and doesn't include the port for your lens.
Many people have differing opinions on great strobes. I'm quite the fan of my Inon S-2000's. They're much smaller, but lack the focusing light that other models do. Other people are rather loyal to Sea and Sea strobes, or Ikelites.
For what it's worth, I shoot a Canon G-15 in an OEM WP-DC48 housing, with Inon tray, arm, and S-2000 strobe. Full rig costs about $1500 and takes some pretty good photos. Good enough that I can't justify springing for an entire DSLR rig for underwater.