PC2700 installed will it play nice with faster ram?

I want to add another stick of ram for a even 1024 but there's a catch. I don't want to buy another stick of PC2700. I'd prefer to be able to buy faster memory for future upgrades.

Can i do this and still run dual channel? I know I'll have to populate the channels properly with the two 256 sticks in the one and the 512 in the other but will I have to buy PC2700? I'd really rather not buy any more outdated hardware if i can swing it.

In addition even if i couldn't run it all dual channel wouldn't it be worth it anyway?

Core system specs: AMD Athlon xp 2700+|MSI K7N2 Delta-L|Kingston Value ddr333 ram 2x256mb|Apollo 9600SE|SPARKLE FSP350-60BT ATX12V 350W

cant run dual channel with 3 sticks of memory. You would need to buy 2 256 sticks if you have 4 memory slots or replace both the 256 sticks with 2 512 sticks of memory.
If you run all three you will have 1 gig single channel.