My suggestioin is to get get your hands on as many cables types in as many price points as you can "reasonably" get your hands on. This would include cables above your "comfort zone" if they can be returned. Expanding the size of your "toy box" makes things a lot more fun, and you’ll get to experience things outside of the scope of "highly recommended" products. I’m going to predict that you’ll find improvements in areas where you least expect it. To me, this is often the most rewarding aspect of upgrades. The price of admission may be less than you budgeted, or a whole lot more. Your internal calculator of value vs performance is the final, and most important, variable.
I would also include upgrading your wall outlets. IMHO power delivery is often the most underappreciated aspect of system performance.
One more thing. I’d consider putting $10 worth of Dynamat on those Heresy horns.