Firestorm

not really worth getting another am3+ cpu. 

You know, it is a good way to deal with most things...

IMO 27" is too big for 1080p at a normal viewing distance ~75cm but consequently you wont be able to see the individual pixels on a 24" 4k but I think it would be the smallest I would go. I use a 24" 1920 x 1200 and it is perfect for me, but 27" at 1440p works just as well. 4k doesn't really have an upper bound for size though. Just my opinion though

This website is very useful for comparing the DPI of different sizes and resolutions of displays

That means the product is by Asus, but the seller is  M H TECHNOLOGIES.

The picture and product name are the same, but the description is for an msi board with the intel socket

XPS 13/15?

XPS 13/15?

XPS 15 has been updated with the same screen as XPS 13 if you want something bigger

Yeah. Its been around for a while now. Chrome users have had the option to opt in the beta updates for ages. I do like it though

Simply take out the card?

Simply take out the card?

Simply take out the card?

I would say Far Cry 3 for a bit of contrast

Its almost 8% of the total thickness of the phone

It depends on what you use for caching and what size it is.
Intel Rapid Storage technology will speed up startup a lot but doesn't really help anywhere else (at least from what i can tell). In my system i have a 32GB cache SSD and a 5400rpm HDD any it doesn't seem faster in everyday use that it was without the cache. An SSHD will actually put programs etc on the SSD so will be faster in everyday use.
 
So: SSD>SSHD>HDD+Cache>HDD

Top one is the regular zotac card
 
Second one is the mini itx version
 
Bottom one has twice the VRAM (4GB)
 
The bottom one will be the best

My personal favourite cheap in ears are the Sennheiser CX-200ii, which sell for around £20 on Amazon for the black version. They sound great, are comfortable but are not below your £15 guideline...
My advice is to spend a little more as they are very durable, my set even went through the washing machine and survived.
 
 
A word on your old pair:
If they are only quieter, it may be because of wax build-up in the grille of the headphone. This was the problem with my CX200s as it turned out but when they (accidentally) went through the wash, the problem was solved.

Tesla is a compute card so will not affect the graphics performance of your system,

I find it very unlikely that you could install android on it. They have different chipsets and apple custom design their own chips so I doubt that android will have drivers for Apple devices. Haven't tried it so there is a very slim chance that it would work.

Yes, yes it is.

RMA that GPU right away
 
I have had two 1TB HDDs fail, RMA'd those!

Dell normally are very good at enabling you to change a hard drive yourself, as a picture of the product page has the bottom removed. It will be a 2.5" hdd as it is a laptop. The thickness is one thing to think about. Best way to find out is by going to device manager, then googling the hard drive model listed under "disk drives".
But.... A better solution may be to add an m.2 ssd as it accepts them, This means you can keep the original storage drive as mass storage.