For the consumer market, nothing with more than 4 DDR2 slots exists. Socket T is for the consumer market.
If you go into the server market (Socket 771 for Core 2 Duo systems) there are currently 21 motherboards that have more than 4 DDR2 slots. Here's the list of motherboards
Of course you would need to buy FB-DIMM DDR2 sticks along with a Xeon machine.
Why do you need 6 DDR2 slots? You can have 8GB of memory on the motherboard already, 4x2GB.