If you have removed the HDD cage then I can't see why that graphics card won't fit.
The HAF 912 is probably one of the better cases at or below $50; plenty of features, good cooling, can fit large CPU coolers and large GPUs.
The RAM will work with the motherboard, but it won't necessarily run at 1866MHz, in fact it will probably default to 1333MHz, you will have to go into the BIOS and do some tweaking and possibly CPU overclocking to get it to run at/close to 1866MHz.
But I currently will keep my 5400rmp drive. Then get a new Hdd not replace the old one I don't want to replace the case either.
Will the fan fit in the current case? I want to keep the drive with windows. Oh and only 800mhz ram work with my mobo (1100 if am2+) I will get a new pay soon and get a 6950 as long as it fits in the case if not I will get a 6850 or 6870