I'm going to give it to you straight.
Canon owners (bwest and I) will say Xt. Nikon owners (latazyo) will say D40. Olympus owners (none yet but they have an interesting and unique system all their own) will say Olympus.
You see, this is a very expensive hobby like reef keeping. Just like a reef, to do it right you’re looking at thousands of dollars. In effect, camera brands are something of a religion.
When we researched and bought our own cameras, for one reason or another the other brands were ruled out and you know what we chose. So in our heads, our camera is the best camera.
I also had Pentax, Sony, and a few others on my original list. Eventually I narrowed my choices down to Canon, Nikon, and Sony. Each individual BRAND has multiple (more than one per brand) dedicated forums rivaling ReefCentral itself in size.
This is my favorite Canon forum, though one of many: (am I allowed to do this?)
http://photography-on-the.net/forum/
On ReefCentral everyone always says "boy I wish I read these forums BEFORE I setup my first tank". Well guess what? "Boy I wish I read these forums BEFORE I setup my first camera" is a pretty common one in those forums as well. Join a Canon, Nikon, and Olympus forum. Browse each for a month+ and then decide which you want. Be smart about it. This is not just a camera your buying, this is a very major purchase with lenses, flashes, grips, more cameras, tripods, tripod heads, tripod mounting brackets, lens filters, computer programs (photo shop, noise ninja, ect., ect.), heck you'll probably spend $100-$300 just for a backpack to carry stuff in.
A DSLR camera is just an empty reef tank. Yes it is expensive but you still need salt water, skimmers, pumps, lights, testing strips, fish, a quarantine tank for those fish, a clean up crew, live rock, corals, ect. ect. ect. A Canon Xt or Nikon D40 are just empty reef tanks...and small 20 gallons at that.
You are making a big decision here. The Company you pick will likely be your company for life (as much of the $1000's you spend will only work with Canon OR Nikon OR Olympus).
Please Please Please think this process out. If you have to ask us what DSLR you should buy, you are not ready to buy a DSLR.