If you're an 'advanced amateur' you should be able to answer this question yourself.
But being as you did ask...
Professional pictures make a pro-photographer not a 'pro' camera.
I would say, depending on the type of photography you plan to be pro at, having a fast lens or two in your bag is way more important than the body. f1.4 or f1.8 can do things on any body that a variable aperture kit zoom never will on a 'pro' camera. Not to say you can't get great pics with kit lens but pros have fast glass for good reason, simple.
However - clients can be as swayed by marketing hype like mega-pixel count as anyone. So could you respond to a client question about your gear, with confidence, with a 24MP FX camera in your bag?