I would go with either Nikon or Cannon. Both companies have vast array of bodies, lenses, accesories and imaging software.
Although we all know Sony produces top quality electronics, photography is not a very large part of thier product line.
Between Nikon and Cannon, I'd go with Nikon. I am a professional photographer and have used Nikon gear for almost 20 years........ so, yes, I am biased, I admit, but I have never had any reason to switch to Cannon.
Nikons are engineered and built very well, and are extremely dependable (just like a Toyota!). I have photographed over 800 weddings in my career and on a typical Saturday night, I'll shoot 2000 to 3000 images. I've had one Nikon body fail one time in all those weddings (we had backup of course). I've never had a Nikon lens or flash fail. Also, my Nikon bodies are made with alot of metal and rubber "O" rings to seal out dust and moisture. In this respect I don't think Cannons are built as well when it comes to being rugged and durable against the elements.
Nikon has 24/7 live tech support by phone. I've never been put on hold for more that 5 minutes before I got a person on the line.
Really, you can't go wrong with either brand. It's all personal preference.
Both companies will allow you to continually upgrade and add to your collection.
You can read alot of reviews (from consumers and pros) at
www.dpreview.com
Just mt .02
Happy shooting!