It's going to be tough to get what you are describing ("a lot of modulation, bass, leads, plucks, pads") from this setup. What you have built is not too much different than a Behringer Crave, which can be found for about $200-$250. I would recommend picking up a semi-modular (Crave, Mother 32, 0-Coast) for these duties and using the palette case to supplement that with more interesting modules like Plaits, or maybe even an E352? An Intellijel Quadrax or DivKid Ochd will give you a fair amount of modulation. Happy Nerding makes a lot of nice inexpensive 6hp modules like a 3xVCA and many more. I would recommend doing a bit more research before you pull the trigger on this rack so you get the results you describe under your price point.
Something to consider.
Have fun and good luck!