Just got done with a 6hr drive and a glass of scotch, but heres my 2¢.
BF3 likes Nvidia cards, so you should probably build your system around a GTX 560Ti, GTX 560Ti 448 core, or GTX 570.
You'll probably be better off with an AMD 960T than an FX-4100, although for ~$1,000 CAD you should be able to get a 2500K build.
Will post a build tomorrow afternoon if someone doesn't drop a viable build before then.
*Edit - Suggestion:
CPU: $230 Intel i5 2500K
MB: $160 Asus P8P67 (REV 3.1)
RAM: $42 8GB Mushkin Blackine 1600/CAS9
HDD: $110 750GB Hitachi Deskstar
ODD: $20 Sony Optiarc 24x DVD/CD Burner
GPU: $240 MSI GTX 560Ti
PSU: $70 Corsair CX600 V2
OS: $110 Windows 7 Home Premium 64-Bit OEM
Total = $982 CAD (-$35 in rebates = $947)
Left out a case since they are personal preference, you have ~$50 for one if you want to count rebates up-front.
I'd suggest either the: $40 Raidmax Reiter
or $57 (-$10 MiR = $47) NZXT Source 210 Elite
*Edit 2 - Found a combo deal.
$220 (-$20 MiR = $200) Corsair CX600 V2 + Asus P8P67 (REV 3.0)
$10 cheaper up-front, but you lose out on the $15 rebate on the REV 3.1 version.
Please read through the thread thoroughly before responding.
Nobody wants to read a wall of text, formatting is your friend.
i5 3570k | 8GB G.Skill 1600MHz | R9 290 | SeaSonic 750X