I didn't disagree with the original parts list that Hor put together. I put the list up using the UK partpicker site, which would give you a price estimate in £££ which it seemed you were spending from your first post, mainly to show the difference in UK pricing vs US pricing (which may still have other taxes but you don't see). Unfortunately the UK partpicker site is missing a few decent retailers, like scan.co.uk and dabs.com for example, so you don't get as wider variety of parts, so in order to get the parts priced, I chose as close as possible. I guess I should have said up front that it was more of a £££ price comparison for a pretty much par for par build.

As for the case. This is always an easy place to save a little cash. On the other hand, I have 3 Fractal Design cases, so I might be a little biased, but I do setup my machines for silence, and have never had an airflow or build problem with them (well, except for a mini ITX that I did once). If you plan on a full water cooling setup, then case will become more important to you, especially when trying to fit in £600 odd of water cooling gear (not including the computer). When using any non-standard cooling setup, you also need to be aware of what the case will fit, and from experience, it is really annoying finding out that you need an extra 2cm. I was careful to select a case which has a lot of potential and configuration options, although it may not suit everyone.


The monitor I suggested for several reasons.
1. I have one and it's pretty decent. I don't know of any 40" 4k <3ms 144Hz@4K monitors out there, so this was my second choice. I read some reviews on it. It was delivered the next day. It Is not a professional colour monitor (which is sad), but I couldn't afford a 40" 4k one of those either.
2. The Wasabi that MiRai has is not quite 4k. It is something like 3802x2138, although I believe the newer refresh is actual 4k.
3. Warranty issues, if you happen to have one, are much easier to sort out when the seller is in your country (although the Wasabi guy is usually pretty good too from all accounts).
4. You can get it cheaper if you shop around.
5. I provided an alternative which is £100 cheaper, although I know little about it, but Iiyama are usually quite decent.


For your existing machine, to upgrade it would almost be a complete replacement of everything in it, because to change the CPU you'd need to change the motherboard, which would require changing the ram, and a new CPU cooler is probably needed (I doubt you have the brackets). You'll want a new graphics card, and you should probably change the 5 year old PSU too, and depending on the vintage of the case, you may find the motherboard cutouts for the back of the motherboard are in the wrong place (happened to me a few years ago when I thought I reuse an Antec Sonata "Piano Black" case). Nothing a angle grinder wouldn't sort of course. Only really leaves putting in an SSD and you've pretty much got what was suggested.