Help building Dual Wan router?

[jammir]

cheapest i can do it and what would i need PC Spec and software?

 

[norm]

Any run of the mill PC, two PCI ADSL modems and your favourite Linux distro. : )

For the PCI device I recommend you use the Sangoma S518 ADSL card and if you're interested in bonded ADSL check out Upstream Internet.

 

[BillytheImpaler]

I agree with the above. for your software choice I think that Smoothwall would be an excellent choice.