From what I can understand from your post is that all of the monitors will project the same image? If so then it’s just like having 2 monitors only now you have 6.
There are a few ways to obtain your objective:
Buy the new ATI HD 5870 Eyefinity which will be an expensive (~$600?) card which has 6 outputs. Should be released next month.
Get 2 ATI HD 5850s (~$200? ea) with 3 ports per card. Released in a few weeks I think.
And the last option is get 3 HD 46XX (or other low priced cards) each card with 2 outputs.
The 3 low priced cards have the cost advantage but will require a motherboard with 3 pcie slots.
Hope this helps