I ride an alloy Topstone and I love it but before you spend money on a new bike I would rent or if possible burrow a bike of the type and price range you are looking at. Then you can have a direct line of feedback to what you would be getting compared to what you have. You might be surprised as to what your current bike has in common with a newer bike or find out that the new bike checks all of your boxes. The Topstone I have is considerably more that your projected budget but you don't have to get a 105 version. I would seriously try to get some seat time on other bikes and see just what you think. You might be better off staying with what you have and saving towards a bike that will make the difference you are looking for.
Frank.