CPU: Intel Core i7-3770K CPU - will save you $250
GPU: 2 X Gigabyte GeForce GTX 670 - will save you $300
Power Supply: Corsair Professional HX850 (80 Plus Gold) - will save you $175
RAM: 1 X what you have should be fine - will save you $137
Motherboard: ASUS P9X79 PRO LGA 2011 Intel X79 SATA 6Gb/s USB 3.0 ATX Intel Motherboard with USB BIOS - will save you $100 ASUS P8Z77-V PRO LGA 1155 Intel Z77 HDMI SATA 6Gb/s USB 3.0 ATX Intel Motherboard - will save you $200
CPU Cooler: Noctua NH-D14 SE2011 - will save you $40
SSD: Samsung 830 256GB SSD or OCZ Vertex 4 256GB SSD - will save you $500
HDD: Western Digital Caviar Blue 2TB HDD - add $125
Net savings: $1602
EDIT: Sorry - I originally didn't change my CPU recommendation but I forgot to update the motherboard choice once I did.
-no reason to run 3x SLI since you dont need it for games. should be only running one monitor
-no reason to blow 4000 dollars on a rig when you are just running off to college. save the money on tutition
-no reason for x79 unless you are doing more than 6hrs of rendering a day
-dont get fisher price watercooling
-1500w is a stupidly high wattage. 750w is more than enough for 2 670s
-3x 660tis is pretty dumb if you ask me
-agility 3s suck. if you want to increase SSD capacitiy, go ahead. ncix has a vertex 4 480gb somewhere on sale. just that if you want to blow that kind of money or not
What canadian retailler would you recommend the most?
DirectCanada is good because they have free shipping and typically have the lowest prices in Canada. NCIX is great too - try to find a retail store if they have one as it's always easier to just pick up the part. Even if you can't find an NCIX retail store, just order it - they have a warehouse in Toronto and its usually pretty fast shipping from Toronto to Ottawa.
So.. yeah, NCIX or DirectCanada because they offer the best prices (usually).
EDIT: Alternatively, you could just go with what the member above me said and use PartPicker to do the hard work for you. When I built my build a few weeks ago - I didn't know they had that so I went through it all painstakingly on my own. I ended up buying most of my parts from NCIX and Canada Computers retail stores because they had great sales and would price-match DirectCanada when they had higher prices. Worked out better for me because I didn't have to wait for shipping and it's always nice to be able to walk into a store and walk out with your parts. Also great in case you have issues with your parts as you can just go to the store and they'll take care of you face-to-face.
If I may make a suggestion as someone who just finished undergrad and is now in grad school, go with a 2,000 rig and get a rugged business laptop for carrying around campus to class with the money you saved. There may be more $ left over even after that and you may want to hold on to it.
Also, If you go 2-way SLI and beef up those GPUs to 670s or 7970, I think you may actually get better performance than you would with three 660s in SLI -- someone correct me if I'm wrong though. The scaling in SLI hits a massive wall after 2 cards. I think the only reason they push 3x and 4x SLI is to squeeze a little more $$ out of the enthusiests.
I just want to give you some advice based on my recent college years. You might want to consider a few questions--Are you going to be living with a bunch of rowdy guys who might drunkenly crash into your compter and break it? Are there going to be parties in your house or dorm? Are you going to be in a dorm room with someone you don't know and might not entirely trust? Are you comfortable having a $4000 piece of equipment in such an environment? Alot of people lead a semi-transient life style for their first couple of years of college--I moved multiple times a year. There are a lot of things that could go wrong by taking an expensive, non portable computer off to college.
TL;DR Dont spend $4,000 on a desktop for college--Instead spend $2,000 on the Rig and spend rest on laptop for school. Chaotic college environment may not be good place for rig.