ok nvm on the gfx card and psu, for the money you probably wont find a better deal.
i really dont think youre going to be needing 8gigs of ram. get 4gigs for now, then if you really think thats not enough, get more. save the money or spend it elsewhere.
and yes, that case from ebay will work. you have to look at what mobo form-factors it supports. the gigabyte is an m-atx (micro atx) mobo, and it does say that it supports that both on ebay and on the makers site.
so it should fit no problem.
you should be good to go.