Hi,
1.Is part number HWIC-4ESW or HWIC-4ETH ?
2.I could not find anything like HWIC-4ETH.
3.After having 2 internet link , you can use them in primary & backup link.
4.Use 2Mbps link as primary link , define default static route to point to your 2 Mbps interface
5.Define additional default static route with higher administrative distance and point to 1 Mbps interface.
HTH..rate if helpful..