CW,
I will make this recommendation since although the consensus to get a better router is a very good one; I will say your idea to switch from DSL to cable is a good one. When they come to your place to install the cable, make sure you are there and ask them before they do the install what are the minimum signal strength to OK your install. Cable gives you the opportunity to make sure of good signal. With any router, gunk in, gunk out.
I will make this recommendation since although the consensus to get a better router is a very good one; I will say your idea to switch from DSL to cable is a good one. When they come to your place to install the cable, make sure you are there and ask them before they do the install what are the minimum signal strength to OK your install. Cable gives you the opportunity to make sure of good signal. With any router, gunk in, gunk out.