Q: A quick question about memory

Hi. I've got some questions about memory.

I'm using a 27-inch, Late 2009 iMac, which currently has two, 2 GB memory sticks and has a 2.66 GHz Intel Core i5 processor.

This page: http://support.apple.com/kb/HT1423#1 says that the maximum amount of RAM I can have is 16 GB: 4 sticks each of 4 GB.

Now, I go to the Apple Store website and look at iMac (Fall 2009). That page says:

"27-inch, 21.5-inch

3.06 - 3.33GHz Intel Core 2 Duo

2.66- 2.8GHz Quad-Core"

If I click on the iMac (Fall 2009), I'm taken to a page with these options:

"27-inch with 27-inch with 3.06GHz (or faster) Intel Core 2 Duo or Quad-Core", and "21.5-inch with 3.06GHz (or faster) Intel Core 2 Duo."

I don't see any mention of 2.66 GHz.

I'm fairly certain my iMac is a 27-inch model. That's what I bought and that's what it says in About This Mac.

Am I doing something wrong? Because I'm really worried about buying memory which turns out to be incompatible with my machine.