As others have stated, the housing is only the beginning of the cost. You will need ports, strobes, arms and cables. The good news is that all of the later moves to a new housing of the same brand (strobes are more flexible even). As for the housing choice, I have always had my DSLRs in Ikelite housings and so far no problems. Some I even bought used here on wetpixel. Take proper care when assembling and cleaning it and all is well. That said, make sure you buy flood insurance. It brings a bit of peace of mind for the worst case and is not all that expensive.
Now if you are not sure if you want a big DSLR under water or rather a more compact system. Check with local dive shops. Some might have systems you can borrow or take a underwater photo class with them they might let you play with their personal system.