Is this good specs and compatible parts for a custom computer?

With an i7 and the video card listed you should be fine. The fast hard drive will help but that much RAM may be overkill for most purposes. The mobo is triple channel so three modules work best so it's either 6 or 12 gigs. Be sure you have adequate ventilation, possibly water cooling to permit overclocking and prevent temperature issues. Some people have issues with that Asus mobo but every product will have some with manufacturing glitches and 4/5 from Newegg isn't bad.