Use Cable and DSL at the same time

I am running Vista 64 and a computer with two NIC’s. I recently added cable service to replace ADSL but I now have both services. Can I use both for increased bandwidth? Ideally, I would like to use one for uploading and one for downloading. Also, my email provider (DSL) requires that I send my email through their server only when using pop access so my new cable service won’t work for that. Right now I have to disable the NIC connected to the cable so I can send emails through DSL from that one acccount. Any software that allows NIC specific routing? Anything in Vista that would help?

Thanks,
Gordo