PC3200 is backwards compatible and will run at PC2700 speeds quite happily.
It's cheaper too.
Here's another thing I was looking at. If you look at the specs of the motherboard it says this:
Front Side Bus (FSB) - 400 / 333 / 266 MHz
PC3200 memory runs on a 400MHz FSB. So I'm thinking that if you use that memory, you can safely run it at it's rated speed.