Personally, the only setup I would build today would be an X79 motherboard with a socket 2011 i7 cpu, 16GB(or 32GB) of quad channel RAM and a modest nVidia graphics card($49 210 will work fine). The rest of your list looks fine but I'm not sure I would bother with the wifi(which should be disabled when running Pro Tools anyway). As for the SSD, that's totally up to you whether the cost is worth the benefits(which I have yet to see here
).
BTW, quad channel RAM means 4 matching sticks
and if a Mac is really what you wanted, don't ignore the Mini i7 server. Pairing that with the UA Apollo would be killer(but a bit over your budget). Other interfaces to consider should include the Focusrite Saffire LS56, Mbox Pro(3rd gen) and maybe the MOTU 828 Mk III.