You really aren't going to be able to shotgun them with the hardware you have on hand. You with either need a much more expensive router or have some pretty good knowledge of linux and routing protocols. (Probably RIP) Even with this you still will not be able to pull the entire "combined" speed in one download as the lines are not combined. All of the requests will come from two different IP's. You will be able to get the down speeds in parralell though.
Jkrohn