[CanonRebelz]

Before you waste your money and get a camera you can't understand, consider some things.
Don't take this personal! But judging by your past threads, you don't seem to know enough to be ready for the full frame camera. So many settings may confuse you if your XTi has already confused you somewhat. The 7D would be too much as well, learn and master your XTi, get some good lenses and save your money while you learn aswell. Read LOTS about photography. Lot's and lot's and lot's. The XTi is a good camera, it should be fine for a starter business of portaits/senior pics etc.
You should try selecting the focus point yourself, you say your photo's are blurry, that is either a few things: your hands, slow shutter speed, or the focal point.

REMEMBER: the camera is only part of what makes the good images, it's the tool, it's the person using the "tool" that does the most part.
Now, I'm not saying you aren't a good photographer, I looked at your website, and they are some good images.