There are a lot of good bikes to choose from in that range. I would suggest going for a hard-tail as opposed to a full suspension in that range because you will get better components and it is hard to find a decent rear suspension until you get closer to $1000.00.
As to which brand to choose, I suggest thst there are two things more important than what brand:
Does the bike fit you and your intended use?
Does the shop you buy from give you the respect and the service you deserve for giving them your money?
Go to as many bike shops as you can, let them know what your budget is and how you intent to use the bike, test-ride as many bikes as you can, ask as many questions as you can, get a feel for who is just trying to get you money and who is really in to getting you on a bike. A good shop knows that good service will get repeat business and probably your next bike purchase.
This is very important, try not to buy any bike on the first visit to a shop. This will help you avoid getting something you will regret later. When buying a bike, impulse buying is bad! Bike salepeople can be just like car salesmen, they will tell you anything to get your money and don't care if it is what you need or really want. There are some very good shops out there with good helpful people, find that shop in your area.
Ride bikes, take notes, go home, compare notes, go back and get the best one in your area for your budget.