Novice RAM / MOBO Compatibility Question

I was just curious if you guys could help me out. I'm about to start building a computer, and I was just wondering if I'm ok using DDR2 1000 RAM in my MOBO with a memory standard of DDR2 1066. I've gathered that it works the other way around, that you can use memory with a lower speed than your MOBO, and it will run with what is supported by your MOBO. I just don't know if it works the other way and I want to make sure before I waste my money. Here's a link to the MOBO / RAM I'm getting.

MOBO: http://www.newegg.com/Product/Prod [...] 6813131340
RAM: http://www.newegg.com/Product/Prod [...] 6820231145

Also, if I can even do this, Would it be that much of a performance downgrade from 1066 to 1000? Should I just stick with the 1066 even though it is more expensive? Any help would be appreciated. Thanks.