First off, welcome to the forum and the sport

!
Second off, I think the Threshold would probably be a good starter bow, with more than enough oomph to take a deer or an elk. I started off with a Martin Saber, which has similar specs, and hunted with it for a few years before I bought a new bow. That being said, you might try the classifieds here or at
www.archerytalk.com to find a good used bow for a decent price. Martin has several nice bows, and you'll find that they are easier to draw even at higher poundages than some of the competition.
Also, FYI, many many hunters use bows that are considerably less than 70# draw weights, one of the most notable is Ted Nugent who swears by a 50# bow. Many speed freaks will tell you that you need to use the higher draw weights to harvest big game, but most states have a 40# minimum. So don't get wrapped up in draw weight and speed at this stage, I think you have a good attitude and start knowing that repetition and teqnique are key to success.
A good rule of thumb is that if you can't sit down in a chair, raise your feet off of the floor and pull the bow back easily, its too much bow for you. This not only will keep you from hurting yourself by pulling a muscle (damaged shoulders are a common theme among some archers), but will make those cold mornings sitting on stand much easier because cold stiff muscles do not always like to pull a heavy string and may make you miss that great wall hanger!
Your best bet is going to be getting your hands on as many bows as you can and finding out what is comfortable for you. You're also going to want to pay close attention to draw lengths, because given your height, you'll have a fairly long draw length. Find a good dealer with a proshop, or a friend that has a firm grasp on the sport to help you get started and you'll be miles ahead of the game!
Obviously those of us here on this forum hope that you join the ranks of Martin owners, so be sure to post some pics if you get one (we love bow-porn). Good luck and good hunting!