I agree with hokiefyd here. The parts are far more expensive than the sum. Unless you have a lot of time on your hands, and the proper tools (crank pullers, various wrenches (torque), etc.) it's probably not worth it. However, buying a used model with good specs is worth it, IMHO. Some good rec's above from hokiefyd.

I also don't believe you would do better with an entry level bike. You'll probably find yourself dissatisfied with the shifting at a minimum, and wondering if you had spent just 200 more for that next step up or bought a better used model, if you'd be happier.