The only thing that is relevant is whether your ADSL modem can be configured as a router rather than a bridge. Almost all of them can, and that is the normal way to set them up these days. Get the model number and brand and look it up online. Better yet, call your ISP and ask them to walk you through setting it up as an ADSL router - any ISP worth its salt should have extensive databases on configuring all the common brands and models to route. Just avoid PPPoE - that is true whether or not you are using LMCE.
Your home network configuration isn't related to any of this - once you have the ADSL router connecting to the Internet on its own, plug its ethernet interface into the external NIC of the LMCE box and set the ADSL router to provide DHCP IP addresses to your core. Then plug your switch into the other NIC of your LMCE box. Then plug your NAS's, PCs, HA, etc into that switch and set them all to get the IP addresses from your LMCE box. You can discard the router, it isn't needed in this configuration.