Granted this is just my personal opinion....

Any of the i7 processors will work great for ya. ( $250.00 ) + ( $ 200.00 motherboard )

4 gig of memory if you plan on running a 32bit version of Windows. If you are running a 64bit version of Windows then you can go above 4gig but more than 4 isn't a requirement to get good performance from Darkfall. ( $100.00 )

For a graphics card I am running an older Nvidia GTX280 with 2gig but the newer GTX260 and GTX275 are good choices but try to get the version with at least 1gig on GPU memory. ( $300.00)

Sadly, all that power doesn't come cheap. If you are building this yourself the entire systems will top out at about $ 1100.00 including a decent case, fans, dvd and harddrive.