Nah, this is where although the question seems straight forward. The answer isn't necessarily so. £1500, Gaming computer..... bang for buck on the graphics... Just doesn't work for me I'm afraid. What I meant was, with the above qualifiers, I goto a shop and select in this order, more or less:
Now I wouldn't necessarily buy these exact items, this is just an example, and I've done it when I'm meant to be working - so quickly, but to me spending £1500 for a gaming computer doesn't show me the client is going bang for buck, imo that is. I mean you may well have the intention to, but I'd not think it necessary. You'll notice I've merely duplicated a bunch of your items from the OP in some cases. In my mind, spending £120+ on a case and settle for not the best gfxcard is crazy talk.
Granted, I've spent all your cash and a few additional pints.