I’ve not read the whole thread but my views (from being “into” hi fi, having designed speakers for a living and also worked in retail” are as follows:
To say that there’s no point in spending more than £200 on any one component is silly. It may be the case in a particular system or where set up is comproimised – but with everything this is a sliding scale.
I wouldn’t buy anything NEW without listening to it with your amp and ideally source. If you CBA researching there are alot of sh bargins on ebay if you want to risk something.
I have heard decent cable make a huge difference – but moreso on better systems.