Dual channel and 800fsb are different things.
Dual channel means you have 2 ddr memory modules working together to provide more memory bandwidth. To do this you need 2 regular DDR modules of the same size and speed. The Abit IC7 will perform either in dual channel mode or single channel mode, it will work fine even with 1 memory module, but if you want dual channel performance you need 2 modules. Logically the closer in performance the two modules the better, some companies are selling matched modules for this reason.
As far as memory speed, the Abit IC7 will work, theoretically, with pretty much any of the common speeds, DDR266,DDR333,DDR400, but it will work faster with faster memory. Also if you are overclocking better memory will work better.
800fsb is actually 200fsb, quad pumped. The motherboard runs at 200fsb, the processor runs at 800fsb. If you have an 800fsb processor it can run at 800fsb in the Abit IC7 with any of the memory speeds I mentioned,in single channel mode or dual channel mode, but the faster memory will of course run faster.