No. You're getting SIZE and 'SPEED' mixed up. These are not the same.
For example: 512 MB (size) of PC3200 RAM ('speed')
The size means your computer can store more information in the RAM instead of having to access it off the hard drive (which is very inefficient)
The 'speed' I mention is the bandwidth, or how much information can be transferred in one second. So if you had PC3200 and PC2700 mixed together, your system would run at PC2700 settings.
Also, don't mix memory brands or sizes in dual channel. This will save you and others a headache. With that board you have I would recommend getting a 2 x 512 MB DDRII 400 memory kit and leave it at that. Sell whatever you have left over or put it in another rig you might have.