To say I was disapointed with this computer would be a gross understatement, the deviations from your description are enormous, and I request the following actions to rectify:
1) Please arrange for couriers to collect the item for return, packaging will be the same as received, and refund all monies paid, i.e. purchase price and delivery cost
2) Refund all costs paid, and I'll scrap the machine for you to save your expense of returning it. I may however be able deliver it to you personally as I pass your way quite often.
You have 48 hours to respond before appropriate feedback and other notification to ebay and PayPal occurs.
Here's why:
This is the package as received. It appears you did nothing to ensure the safety of the contents, as a consequence the box was literally falling apart, with some components such as leads hanging out of the numerous holes in the box.

During it's numerous impacts in handling the rear of the computer has been compressed, causing the breaking off of the Wireless networking card from the motherboard, I've not checked at this time but the socket on the board might be damaged as a result.

Because you rested the computer case on top of the sub bass unit in the box, it dented the computer case over a large area:

So from a handling point of view a failure on all counts, all due to inadequate packaging, not the cause of the carrier. Pause now and take a look at the condition of the case in general. Your description read: 'I am a system builder', 'The case is second hand and therefore has a few wear and tear marks on it but nothing really noticable', and: 'I have cleaned it up and am very impressed with it' .
So this is your idea of a cleaned case?:



Clearly you have delusions about your skills, or you're just a blatant liar, that's up to you to decide, but as a 'system builder' how do you justify this:
None of the cd drives are connected with either power or data cables
There are no data cables for the cd drives installed at all
None of the front panel cables are connected to the motherboard


You stated:
'All you need to do is plug in your keyboard, mouse and monitor and it'll turn on as normal!'
To apply power to this pile of scrap would be a waste of time, so I have no interest in proving whether the bits that are connected work or not, but that's academic anyway, you've sold me scrap parts unfit for the intended purpose and there is nothing you can say to defend or justify your actions. I've not looked at the messed up boxes that represent the sound system, clearly such further effort on my part would be pointless.
So the choice is yours, remember you have 48 hours from the time that the email linking to this page was sent, no excuses, before I take appropriate action.