Where’s My Weakest Link?

FWIW during the early 1980’s I purchased a Carver C-4000 preamplifier, which included sonic holography as well as some of the other functions that are provided by your C-16, while selling for a considerably higher price than the C-16 (which I believe was introduced toward the end of that decade).

After a few years I replaced the C-4000 with a Mark Levinson ML-1, which resulted in a truly "night and day" sonic improvement. So after doing a bit of research on your other components I suspect that your preamp is the weakest link.

If after replacing the C-16 you want to retain the sonic holography feature you should be able to find a C-9 at very low cost.  The C-9 provides only that function and is used in conjunction with a separate preamp. I didn’t miss that function at all, btw, after I started using the ML-1.

Also, I believe your power amp is nearly 20 years old, and so it might be approaching the point at which significant degradation of the capacitors in its power supply will be occurring, if that has not already started to occur. Its present market value appears at best to be in the vicinity of only $500, so when and if its electrical condition seems to become an issue replacing it with something else, rather than having it overhauled, would seem to be in order.

Good luck. Regards,
-- Al

The Node 2i. 

@otterbein  - I suspect Al is correct. The Carver pre-amp would be the first component in your system that I would consider replacing. Again, if you use, and like, the sonic holography feature, you could look for a free-standing Sonic Holography processor to add back into your system. Also, considering the age of your amp, you might want to consider having the caps replaced for many more years of reliable enjoyment.

If you want to consider a more radical change, you might consider a nice quality integrated amp to replace both your pre-amp and amp. There is a Rega Elicit-R for sale now on A-goN for $1175. That's the lowest price I've ever seen for this model (which I own). And there is a Rega Elex-R (Less power than the Elicit-R) for only $699, but it has some scratches on the top cover plate. Anyway, both of these units would be nice simple replacements for both your pre-amp and amp, and provide a remote. Just another option.....

Enjoy the search. Don't get overwhelmed with the options. You have a nice, simple system. If you like the simplicity, stay that course and just upgrade one or two of the components. 

You mention your cables are "generic" like Amazon Basics generic, or some such? Cables can make ALL the difference. You don't have to spend thousands (though you could). A good start is power. Like MC said, do your outlets, easy and relatively cheap. Then power cables. Lot's of options. Look within your budget, check the a-gon ads etc. Then look at your speaker cables, same thing. Last interconnects. See what you wind up with. Keep in mind cables are a slippery slope. Once you have a set of cables that work well, then think about maybe upgrading components. Then, if you want from there, tweaks. And yes, the room can absolutely be everything. Very important. 

@almarg has presented some very relevant facts. The OP has aging components that should be addressed first. Plus, I doubt that his amp and preamp are revealing enough to warrant adding tweaks such as aftermarket outlets and power. 
Building the foundation of the system should come first. As stated earlier, an integrated amp would be a good way to go.