Absolutely not losing anything. In fact, you may be improving things. You can get the same sound with the regular setting, I believe. LFE+Main would run LFE through the M60s, which is not necessarily a desirable thing. Most people set the crossover at 60 or 80 when using the M60s, and leave the speaker set to small, so the bass from the main outputs goes to the sub, not the speakers.

I am the Doctor, and THIS... is my SPOON!