Where are you located?

Ah yeh thanks, have updated the post

@shapenz - Any chance of another one of those SFF desktops? I now have another kid wanting to get into pc gaming - bloody expensive lot.

Bit of a dremel and do this? The $69 Gaming PC RETURNS - Bing video

I have an rx580 I'll be getting, reckon it should be ok.......?

requires 1 8pin pci connector

Actually just checked out the manual - they are not screwing around - there is not much room in those units:

OptiPlex 7040 - Small Form Factor Owner's Manual (dell.com)

Might not be a go for me sadly

Some of those SFF can easily be re-housed in standard gaming case with all the ARGB bling etc.  For example, I put a 
HP ProDesk 600 G1 SFF in a standard case and all the stand-offs etc lined up (no dremel required in this case).  There's adaptor cables available if you want to put a bigger power supply in.

CokemonZ:

 

@shapenz - Any chance of another one of those SFF desktops? I now have another kid wanting to get into pc gaming - bloody expensive lot.

 

tim0001:

 

Some of those SFF can easily be re-housed in standard gaming case with all the ARGB bling etc.  For example, I put a 
HP ProDesk 600 G1 SFF in a standard case and all the stand-offs etc lined up (no dremel required in this case).  There's adaptor cables available if you want to put a bigger power supply in.

 

As good as re-casing an OEM build might sound from a value perspective, there really are a number of issues to contend with:

1 - As already pointed out, a new PSU with suitable wattage and the necessary PCI-e connectors is needed.

2 - An adapter for the above PSU as the OEM motherboards often use non-standard power connectors.

3 - Non-standard headers for: CPU and case fans, front audio, USB, USB 3.0 (which look standard but wired differently), power/reset switches, hdd/power LEDs.

4 - Motherboard mounts are usually standard, (but not always), but sometimes the mount for HSF is built into the case, as is the I/O shield...

All this is deliberately done by the OEMs to stop people doing this sort of thing.

If you're looking for a base for a gaming PC, (say everything but the GPU), flick me a PM, (I build gaming PCs as a side hustle). I can easily build something to spec for the kind of GPU you want to run.

Also often the OEM cooling solution is tied into the case airflow more than a standard cooler so needs replacing as well. At the end of it you have a whole computer that has an old CPU in it and a motherboard that will have crap bios and possibly runs at a lower power limit than a normal board would do.

An aliexpress board is often a better bet than using the OEM board but then you are getting close to just buying a new i3 and cheap new board pricing. And a modern i3 will whip older i7's and take current ram and PCIe etc.

Any interest in a Lenovo M73 SFF?

8GB RAM, 256GB SSD, I think also 6th gen Intel CPU

@tangerz Thanks for the offer - but was really after a cheapie and $150 was a deal.