It seems you have a fair amount of needs/desires/places to step your rig up.
Mistakes Ive made in the past surrounded my lack of perspective usually. Like my thinking OOOhhh, this rig is it for me. Ill not be making significant changes soon.
But I always either did, or wanted to well, earlier on for sure.
So instead of thinking in terms of bang for buck with this one amount of freed up pesos, perhaps thinking along the lines of where you want to wind up would be more beneficial in the long run.
I'd begin looking into power cords. Front end and back end, primarily. Source & amp. As your source could be and likely will be upgraded at some point later on, I'd focus on the amp's power cord needs now.
A pretty nice PC there will yeild sufficient enough results so that you'll feel you have bought a new amp! A friend brought over his 1080 for me to try in my system and simply by exchanging my PC for his on the rotel, he was quite impressed.
Check out a Voodoo Gold Dragon, Kimber Paladium, Audience, or Shunyata Taipan, depending upon which way you want to take the presentation.
Ive always found once aftermarket power cords are in place the systems voice is better revealed or allowed, if you will. So Im big on pcs in general as a formidable path to step up performance. They make for a great foundation or reference and will apply to other likewise devices too later on.
With those 9NTs, which I had some years ago myself, some nice speaker wires there will be a true plus. I liked Synergistic Research. I tried a few others too, Purist, Wireworld, Audience, Vampire, Monster & Canare. From where you are, some nice well heeled neutral cables there will last you thru more than a few upgrades elsewhere and allow you to hear those upgrades for what they are too!
It might not seem fun to drop $500 into speaker cables to you but it could very well contain a whole lot of wisdom.
Thereafter, looking into the cable loom including your digital link should be addressed as you can. Obtaining a good pr of main ICs should be the first move there IMHO.
Maintaining signal integrity via the wires in place is always a great idea.
RE Power strip?
Its difficult to ignore for sure, especially if one is required, and Id suggest you definitely look into getting something other than that Monster gizmo.
If one is needed insert a PS Audio Duet for instance, or something else around the $200 area that the Duet goes for these days.
As was said already, a better unit here will do you a better job and better here means pretty much, an investment of more than $500 if you plan on attaching all the system components. Running Springs Audio Haley is a safe bet, though they range about the $700 or more plateau..
But even little things now can add up for you, like isolation footers for your source, pre or amp. Different spikes for them 9NTs too will help maybe even a platform for them too!
Itd be a good idea now to enable yourself to hear the upcoming changes so speaker wires and power cords ought to gain some serious consideration.
Hope this helps.
Do have fun.