Connect cable modem to DSL router.

I had to look up the product you mentioned. The reason is that "DSL" is a group of standards for digital connection overlaid on the telephone line, which obviously requires a modem to work...
So, when I see the term "DSL router", I think of a box that combines a DSL modem and a "home router" in one unit. In such a unit, the "upstream" connection is a phone line. But you need a router, where the uplink is an ethernet connection.

Now, if you have problems with dropped connections, then there may be several reasons for that, especially if you're using wifi. If you're using channel 4, and your neighbor is on 5, then your networks will disturb each other.

You can use Metageek inSSIDer to check the wireless environment in your location. It is better to share one common channel, than using adjacent channels.
The general recommendation is to use only channels 1, 6 and 11, but many routers just pick a random channel and you may need to adjust to the reality.

Some routers with limited memory may also have problems if you're using a large number of concurrent connections, for example torrents with DHT.