Fuse and Power Cable improvements 'how'? - Nuprime ID-8

I have never heard either, but I bet you could buy the Yamaha for around the same as you could sell your Nuprime for...if hopefully you can audition it in your system.  It's lower power but you might like it better...but I stil stick with the give the Nuprime another month, then with tweaks it might be perfect...

sometimes the change from break-in is quite significant, sometimes not

So many review-bought disappointed audio gear heads turning to cables and fuses to turn a sow’s ear into a silk purse. 30% of the price is ludicrous. Dump the amp or speakers and start over. Or realign your expectations. 

I heard the Kudos C2 in a dealership in Austin, TX. Thought them to sound very good to me. They were driven by a Mystery Tube integrated amp, Not a 100wpc amp. I would reconsider the possible lack of synergy between amp and speaker.  

I don't think power cables or fuses will achieve the results you are looking for. Most people who enjoy improvements with these upgrades are in measures of resolution. More air around instruments, more precise soundstage. They are not going to increase the sense of power or bass slam. 

I recently went through the same issues. I bought these huge Legacy Focus speakers, who claim to be easy to drive. I used a Forte' 200 watt amp. And experienced the same feelings you are having now. Lack of energy, running out of steam, doesn't sound like the amp is doing it. So! I added a Crown class D amp that delivers some 475 watts! And bi-amped the speakers. A bit better, but still not cutting it. With all those watts, how could it not deliver? So, fast forward a few years and I bought a used Krell FPB-300, less power than the other two amps put together, but wow! Now this amp is doing the job! Jaw dropping improvements, bass slam is incredible! Midrange and treble is smooth and articulate. 

My moral, or point, is that wattage can be a misleading rating. How much current can it flow? What is the slew rate? These are much more important numbers than wattage. A 50 watt Krell can out perform many 200 watt amps. I've heard that the 150 watt Pass Labs can drive huge speakers with ease. How to tell which amps deliver, and which do not? Well, short of listening to them at the salon, a study of the specs for the current ratings and size of the transformers, reviews that use words like slam and punch. Capacitive storage in the amp. And it's ability to double down as speaker impedance halves. I.e., 200 @ 8 ohm, 400 @ 4, 800 @ 2, etc. is a good sign of real power.