NEW CAD/Gaming rig

Approximate Purchase Date: Likely next week

Budget Range: $2300-2600 CAN

System Usage from Most to Least Important: Design programs(AutoCAD, solidworks, programming, Maple Sim, Mat lab, circuit analysis software), gaming, movies

Are you buying a monitor: I have a 1920x1080 monitor

Parts to Upgrade: Everything except peripherals already got mouse, keyboard, headset, monitor and speakers.

Do you need to buy OS: Yes

Preferred Website(s) for Parts: Newegg.ca, tiger direct, amazon

Location: Ontario, Canada

Parts Preferences: Nividea GTX 680 for GPU and an i7 processor. Undecided wether to get water cooling or just use fans.

Overclocking: yes

SLI or Crossfire: maybe

Your Monitor Resolution:1920x1080

Additional Comments: would likely prefer water cooling since i will probably be overclocking and getting a second gpu or upgrading it in the future.

And Most Importantly, Why Are You Upgrading: Have an ancient 5 year old lap top that is as slow as molasses, need something that will last me a good 3-4 years.

This is what I am looking at so far:
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Case: Corsair Obsidian 800D/ NZXT Switch 810/ up for suggestions I want a big sturdy case with lots of room, good cable management and possibility of water cooling.
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CPU: Intel i7 3770 ivy bridge / up for suggestions here but I am looking for performance
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GPU: Nividea GTX 680 (only planning on using 1 monitor, might upgrade it in the future to a bigger higher resolution one so a quality GPU is in my best interest.)
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PSU: Not really sure, I was thinking a 750W with a gold rating one for future overclocking and SLI.
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HDD: at least 1TB and probably cavalier green or baracuda brand
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RAM: looking for 16G of RAM and it has to be low profile
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SSD: enough to hold my OS and maybe a few programs(80-120G)
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Optical Drive: Blue ray player/writer
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MOBO: Not sure but it has to be compatible with i7 and GTX 680
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Cooling: Not really sure if I will need extra fans or water cooling kit, suggestions are welcome.

random things: Dust filters for fans and maybe thermal paste