[FRpilot]

I just built a sff pc. it's expensive and those cases you pointed out are not sff, they are mini towers. mini towers are small though, but taller than sff. generally, sff will only accept matx or iatx board, i'm pretty sure you can put a regular atx board in those mini towers.

sff do run hotter since there is less space. the heat in mine where the gpus are position is especially hot. i can feel the heath through the plexi window, but the cpu/memory side is cooler. you would want to get a full modular psu and only plug in cables that you will be using, so there won't be a rats nest clogging your airflow. lots of fans should be considered too.

btw, i7 could be either a p55 chipset or x58 chipset. i have a i7 860, but it is a socket 1156. p55 is recommended because the mobos are generally $100 cheaper than x58 mobos and fit your budget. and stock for stock, an i5 750 runs as fast or faster than a i7 930 according to most benchmarks.