A good list; here are some thoughts for you:
1) For gaming, the graphics card/s is all important. The GTX560ti is appropriate, but consider shifting more of your budget here if you find savings elsewhere.
2) I see some confusion about sli and future upgrades.
In my opinion, a single good card is a better option when it will do the job. Only if you are looking at triple monitor gaming, or a 2560 x 1600 monitor would dual cards be appropriate.
To plan for sli, you will need a more expensive sli capable motherboard up front, and a more expensive psu.
To my mind, I would save the difference to get a better card up front. The upgrade plan would be to sell the initial card, and then get the next best thing.
At the end of the year, the 28nm cards will appear, making them cooler, faster, and cheaper to produce. It will not make much sense to pay top price for an obsolete card for sli.
3) Since there is only a small price premium for a Z68 based motherboard, I would go for that.
4) Is there some reason you need windows 7 professional? Most home users only need the features in home premium. Go to the windows 7 web site to see a list of differences.
5) Seasonic is one of the top brands, along with Antec, Corsair, XFX, and PC P&C. 550w is appropriate for a GTX560ti or a GTX570.
If you are planning on an upgrade, consider that :
GTX580 needs 600w with 42a on the 12v rails plus one 6-pin and one 8-pin PCI-E power lead.
GTX590 needs 700w with 50a on the 12v rails plus two 8-pin PCI-E power leads or 4 6-pin power leads.
XFX currently has some of the best pricing.
Look at this 650w unit for $60 after rebate:
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
6) Of the two motherboards you listed, the cheaper ASUS is a micro atx board. That's fine, but with only 4 expansion slots, any sli configuration will have the two cards located next to each other. That will make the top card run much hotter. I see no need for a very expensive motherboard unless your objective is record seeking overclocks. For the gamer, a simple OC to 4.0-4.5 is all you need. Any Z68 motherboard will do that.
How about this Asrock for $115? It is the budget brand for asus.
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
7) The Zalman cooler is pretty, but I don't like it. It is less effective than larger tower type coolers, and a 92mm fan will be noisy when it spins up under load.
The Xigmatek gaia will cool better, be quieter, and is cheaper:
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
8) Cases are a personal thing. Get the CM if you love it; you will be looking at it for a long time.
But for pure functionality and quality, look at the Antec 300 illusion model for $70 with free shipping . There is a reason for so many glowing reviews:
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
9) Gan you fit a 80-120gb SSD in your budget for the OS and apps? Everything you do will feel so much quicker. Expect to pay $1.50 to $2.00 per gb.
10) For your first build, I suggest you download and read, cover to cover, the manuals for your case and motherboard. Now. Many questions will be answered.
-------------Good luck-----------------