Hey well I'm a Noob but I'll help you out all i can, first you need to list all your other components. And as for the GA-Z68X-UD3-B3 it does not have the Lucid Virtu feature. Also is it worth paying 200 dollars for a motherboard? Well it depends on what components and feature you need.
Ok based on the motherboards you choose The two Gigabyte motherboards only have a single slot in between the Pci 2.0 so if your going to sli your not going to have good air flow. Also are you plan on using the feature that z68 motherboards offer if not P67 will be sufficient. But if i would have to choose a z68 motherboard i would get a MSI Z68A-GD65 . It offers good overclocking feature plus is a little cheaper than the asrock. And also for the gigabyte motherboard they are more mainstream boards they don't have all the power phasing and drmos feature that the Asrock or the Msi motherboard i suggested.
Your original choices are pretty good. So here's tips on various parts that you don't actually need. You're in the same boat as me--can afford whatever is worth getting. I'd actually try to save some cash here or there and put a OCZ Vertex 3 SSD in the build though, it'll improve the impression the new build gives you.
$190 GIGABYTE GA-Z68X-UD4-B3 http://www.newegg.ca/Product/Product.aspx?Item=N82E1681...
If you have no cost limitations, I'd get this one. It's very similar to the Gigabyte I linked on Newegg.com with the 12 Phase power design, it SHOULD overclock like crazy...but I haven't used it personally.
RAM: So long is it's 8GB (2x4GB) 1600CL9 or faster, you're good
PSU: Your Seasonic or any Antec, Corsair, or XFX. 750W would be adequate for SLI'd GTX 570's.
Graphics: $330 Any GTX 570. I'd go for the Asus DCII because it supposedly overclocks better or one of the XFX ones with lifetime warranties.
HDD: Samsung Spinpoint F3 1TB. It's as fast as a Caviar Black, but much cheaper. On Newegg.COM, it's $50 right now. I don't know how to get it to Canada for cheap though, sorry.