The most important thing when trying to do high sound quality on a budget is to understand it is always all about compromise, and then figure out which compromises you are most able to afford and live with.
For example, the path you are on looking for Quicksilver monoblocks the compromise is it is not a budget path. Separates have all the same needs as any other component- interconnect, power cord, springs, etc - but for all that you get only a power amp. Very good choice if your system budget is into six figures. Very poor choice if it is in the low four figures.
The other tradeoff people make is quality. Low end budget gear falls in this category. You get tubes yes, but they don't sound very good because with tubes quality is what it's all about. Not just quality of tubes either but quality of transformers, caps, and other components even more so. Sometimes the quality compromise is they are not very good parts, other times it is just they are not very well made.
There is a third tradeoff, and that is for you to put a whole lot more effort into understanding what is going on, prioritizing your personal needs, and then making a hard cold choice as to what really matters to you.
If you can for example compromise on speaker choice, instead of buying whatever speakers you like and then trying to find an amp that will run them, you might choose only very high sensitivity speakers. Because they don't cost more, but they save you money by not needing a lot of watts. Then you find there are very low power tube amps that sound absolutely divine, do not cost an arm and a leg (because, low power) and really the only compromise is not high volume or great earth shaking bass.
It is always a compromise any way you go, and yes any amount of money too. You already put yourself in a box with those Monitor Audio speakers, at only 90dB they are too low for many amps that would be an absolute dream had you only known to buy something like Tekton Lore Reference. At half the price, but 6dB greater sensitivity they cut your amplifier wattage needs by 75%. Yes you need only 1/4 as many watts to drive them to the same volume as your Monitor Audio. Sound better, too.
If you are in love with those speakers, great. Just know they are forcing you to consider only high power amps, and those cost money. Low power amps you can get the insane good sound you seek, just not from those speakers.
https://tektondesign.com/product/full-range-speakers/mid-towers/lore-reference/#colorWith those you can run this, and it will play Lore as loud as your current speakers will with 50 watts.
https://www.decware.com/newsite/SE34I.htmSee what I mean about compromise?
