"LFE" is "strange terminology"... LFE (low frequency effects) is
normally the "point one"
channel in surround format and it doesn't include "regular bass" in the other channels. The LFE gets routed to the subwoofer ONLY so if you don't have a sub you lose the LFE.
AVRs have a built-in crossover and "bass management" options so the bass from all channels can be mixed and routed to the sub. And of course that includes regular 2-channel stereo sources. Usually that's called a "small speaker" setting, and it's the most common home theater set-up because most people don't have room for 5 or 7 (or more) full-size speakers that can reproduce bass.
Usually the easiest & best solution is
get an AVR, which will have the full crossover with high & low pass. Or, many people just run full-range into the main speakers. You can also buy an
active crossover or a MiniDSP. But, you still need a proper surround decoder and bass management
if you want to get the LFE from surround tracks and mix it with the regular bass.