Two internet connections on one network

I have a question about running two internet connections on one network.  I did some seaches and found this question usually with people trying to increase bandwith. to be honest I just want to be lazy and have it use which ever one is there at the time without reconfiguring the rounter and IP aaddress.  Situation is I have cable modem and a DSL modem and I sometimes swap services.  I have to linksys E1000 rourters and currently have them set up as 192.168.1.1(cable) and 192.168.0.1(DSL). I usually only have one serve turned on at a time.  If have not figured it out already I swap services to stay in promotional rates.  I would like to have them both hooked up at the same time and have the network use whichever internet is working at the time.  I also have a Linksys/Cisco SR224G wth 2 1gb ports on it if this help at all.  Do I need to buy a dual Lan Router or can I work with what I have.  Networking is not my strong point so you may have to ask me more questions to anwer my question.