Find a "rescue" for a great pure bred dog, at an affordable price. Sometimes you have to search CL, but can find a great dog there. As others have said, if you get a pure bred, well, you get what you pay for....
If you want a damn good, and easily trainable dog, get a Doberman. They are not naturally mean in any way, and have to be trained to be like that. They are the next dog on our list as soon as we move to Texas at the end of the month. The public opinion of them as a "mean" dog is completely skewed by the media, and movies. They can be trained to do pretty much anything though, and amazingly great guard dogs is one of the best things to train them for. Of the 3 major lists of dog breeds, and intelligence testing, 1 list has them as the sixth smartest dog, and the other two list them as the smartest of all dogs. I am getting an all natural Doberman, no cropped ears, and long tail.
Also, last time I checked, there were quite a few people looking to sell their papered (purebred) Dobermans of CL for $300 and under.