Exactly what are you trying to accomplish.  Are you going to use your PC as a server?  Will it be on all the time? 

If you have two links from your broadband provider, unless they have separate paths from the provider to you, redundancy on the line won't do much good - if the link goes down without complete redundancy and allternate routing - when one link goes down the other will most likely go out too and redundancy in that case is out the window.

I had "redundancy" on my commercial links but it was complete redundancy including two different local access carriers from the AT&T central office to my computer center.  e.g. one link was via the local bell telco that "penetrated" the building from one street, the other link came from a local fiber optic provider that "penetrated" the building from a different street.  The two different providers came into the computer room on separate cables and thus complete redundancy from AT&T to/from my computer room (Network center).  Also AT&T had separate paths from their central office in my city to the distant end for the circuits thus providing complete redundancy.  However, this was a Federal Government network and redundancy was a must to provide 100% up time.

Unless you are willing to fork over lots of  $$$ for something like this, just having the one lbroadband link is going to suffice.

I'm going to have a DSL and Cable connection to get redundancy.  My cable will be my main one but as stated I want to have the DSL kick in after it is auto detected that the cable has gone down.  Pretty cheap exercise in that it is either a $15 NIC or $130 dual-wan router and the monthly carrier costs are modest.   I just am not sure how to best execute it.  Also, I'm not on a network so this is a simple standalone machine. 

I'm not sure how you can implement auto routing (between the primary and secondary paths).  However, for a "simple standalone machine" (home PC) I wouldn't even fool with it.  You must have lots of $$$.