Worth upgrading my cables?

You would absolutely benefit from changing your speaker cables to Morrow, but I would at least go to the SP-4's. I had SP-6'S and sold them because I needed a longer run. I replaced them with Canare 4S11's and everything completely collapsed! Presence, soundstage, details and it sounded like the speakers were shouting music at me instead of placing music in the room. Now I'm completely satisfied with Morrow (SP-7's) speaker cables back in my system. But like I said, SP-4'S is the lowest I would go in the lineup, as I have gone through this before. Throughout the years I have had SP-4'S, SP-6'S and now SP-7'S. My interconnects are Dig-4 and MA-7's. And I promise you that even after months of use, they keep getting better! For power cables, I have all hospital grade 14awg from Amazon and I'm happy with them. The only cable that I will eventually replace is the Dig-4, and I'm going to replace it with the Acoustic Zen MC-2 since I hear so many success stories about it. Have a great day and enjoy the music! ✌️

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.

Assuming that you have solved, power distribution, speaker positioning, turntable/ cartridge alignment, components support, any room treatment (if needed), then better cables, no matter if silver or copper, will definitely have a positive effect. Everything matters for achieving a good sound not just cables. You can find a good and reputable dealer and borrow complete sets to try out, and save money in the long run. I have a sweet spot for cables that use means of better conductor manufacturing process so that leaves out for me the majority of the pro called cables. In an era of Triple C, Ducc or even OCC (all of them having advanced methods of manufacturing), the ones using OFC are lacking. But good sound of a cable is not only determined by its conductor but by its overall construction, the materials used, the geometry and the connecting component.

After trying out and experimenting you can only decide what is good for your system.

So many folks here have fine quality components connected with less accomplished cables. Mistake every time!  If you need convincing, then do it. Research cable offerings, make a short list of those you would like to audition, and listen.  If you don’t hear ANY differences then you are at a point with your system where it is incapable of revealing cable variances. If your music satisfies you then you are at a good spot and should just relax and enjoy what you hear. 
 

If you do hear differences, the real work now begins. What cable sounds how in what system connection?  What combinations of cables in specific connections, improves the sound of your music?  The one real limiting factor is cost, assuming you have a limit on the funds you can allocate to your cable project. 
 

My last five system purchases have been cables. Four were power cables and one is the interconnect between my line stage and power amp.  
 

one warning…don’t even go there if you can’t afford the cables you audition. You can’t unhear what the auditioned cables brought to your system. That just leaves you with a persistent reality of loss.

Thanks to everyone for the helpful suggestions. It sounds like it is worth investing some better/different cables to match my system. This is not to say the cables are the be all end all, and that as always placement, room treatment, component synergy, etc. are all critical factors to consider as well.