You may benefit from a (small) SSD for the boot drive, for the price of the investment it will give unbelievable speed boost. You could then get a WD green 1TB for less or 2TB for about same, then put the things that you don't need the extra speed for Movies, Music, etc. (Note: [FROM WHAT IV READ], only the start up speed of games will be improved from SSD. So could put them on the HDD too.)
Also I would recommend putting the money from the mouse and keyboard into a 780 or equivalent instead, then look on ebay or local second hand store and getting some cheap one instead for less than nothing, they will work just as well and still out live many other parts of your computer. Some will disagree but from my own experience iv never had to replays a mouse or keyboard. a keyboard is a keyboard, and if the mouse has two buttons and a weel your set.
If you wont a nice/new keyboard/mouse then go for it, but if you could instead get a better GPU.... up to you.
As for a mother board Im not sure, but I will say wile you shouldn't cheep out too much; a mobo is a mobo, get a good one but money is better off going into a better GPU.
Hope this helped, but wait for more responses as Im not an expert.
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