My recommendations, and my narrow biased opinons: (none of this is meant as a personal attack, just 25+ years of PC experience talking)
Intel Desktop board. (as in, Intel brand, not a clone board) something like a DZ77BH-55K or newer
Fastest RAM you can afford without overclocking.
Fastest i3 CPU you can afford. (i3 2130/3240 or similar)
Intel 520 SSD, in whatever size you can afford.
The only thing an i5 or i7 is going to get you is 6MB or 8MB of CPU cache, instead of 3MB you get with the i3. Yes, it will help, but not significantly enough to warrant the price jump, imho.
There's no point in have 5 or 7 CPU cores idling while you play DF. Just a waste of money and electricity.
Also, context switching will reduce DF performance. Once you get over 50 processes,
DPC/ISR latency alone may be enough to introduce human-noticeable latency, depending on your hardware.
In other words, you'll be better off buying an Inspiron 15 model 3521 i3 Dell Laptop for $380 and replacing the HD with an SSD ($100) and dedicating it to DF, rather than having a computer running 70+ processes at once.
For reference, WinXP requires as few as 12-14 "operating system" processes to run any game you'd care to play, today. Similarly, Windows 7 can be run with as few as 24-28 "operating system" processes and perform the same role. If you restart your system, login, wait 5 minutes, and look at your current list of processes from all users on your current computer, and it's over 20 on XP or over 30 on Win7, your system is not tuned for gaming. It's tuned to be slow.
A properly configured SSD gaming machine, running win7, since Jan 2012, should start up from cold power on to login screen in 6-10 seconds. Even if your current HD based PC takes longer than 60 seconds to boot up, you should educate yourself on how to fix that before you go spending money on new hardware. Nothing worse than seeing good hardware go to waste!