So as I move into my 3rd year of photography, I find my 500D isn't able to help my take my photography to the next level and its beginning to feel like my L series lenses are begging to shoot on a full frame body.
Buying better gear won't make you a better photographer!!!
The technical IQ of your fotos will improve if you go FF, but it will not help you to improve your composition and lightning, it won't help you to find a creative angle, or to press the shutte just at the right moment. Technology has a habit to go into the way of creativity.
I just moved up the cameratree (no not to FF, just to a better APS-C). I bought a 70D and sold my 350D after more than 7 years. Did the 350 hold me back? No not really; there where situations where the 350 could not keep up with the circumstances (low light, fast moving objects); I missed some shots, but I knew why I missed them, and it was not about me, it was about the camera.
Fact is, you have to learn to live with limitations, even if you go for a 1DX there will be limitiation of what the system can do. I suggest that instead of spending a lot of money for a new FF body, you should spend the money on some books about photography, or you try to shot more with the system you already have and learn more about that.
By the way, is there a way to see some of your work?