Where’s My Weakest Link?

@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.

Don’t replace the Node 2i, it is very nice little streamer that would cost three times its cost to exceed. If anything, in the future you might consider adding a stand alone DAC, but again, multiples of its cost for any real benefit.

There are other things to consider first.  After any basic (and needed) hardware changes, I would buy Canare 4s11 speaker cables and Canare L-4E6S interconnects from a vendor such as Markertek or Redco.  The total for the above very nice cables would be very reasonable cost.

Between your ears. Seriously! Put yourself in a better mood and your system will sound better. Otherwise, get two subwoofers and a 2 way crossover.