Subwoofer Connection

I'm currently running my subwoofer via the LFE-Out on my pre/pro. All my speakers are crossed-over at 80 Hz. I'm considering re-wiring my mains so that I use the built-in crossover in the Sub. My thought is by doing this, I can listen to analogue music and still have bass management (my pre-pro has to reconvert the signal to digital for bass management).

My question is this: By running mains through the sub, and redirecting LFE to the now "large" speakers, will there be any practical difference in the sound? I.E. will movies lack something because the LFE will now be redirected to the mains (with sub)?
Yes you will miss something unless your DSP can take the 0.1 channel and "phantom" or mix the signal with your front L & R channels. You will also might lose the ability to use effective notch filtering on your extreme LF base...which almost all rooms require.

Some DSP's can solve this for you by offering separate bass management features for both two channel as well as handling 5.1 and other digital formats (like Anthem)...this often requires A to D conversion of analog stereo inputs. If you can't hear the difference from this additional A to D processing step (like most people) but you can hear the difference in improvements from effetcive bass management adjusted for room (like everyone)....then go fo this solution!
Surely it will sound different. Better? Worse? Who knows. I would suspect that, if improving the two channel sound is what you're after, this may not be ideal. Simply because the crossover circuit in the subwoofer will probably have a negative impact.

I believe you are correct in suspecting a loss of bass impact for movies. Depending on the Pre/Pros re-integration of the LFE channel.

I digress, everything in audio seems to be, in the least, a tradeoff of some magnitude, even if it is minuscule. Having said that... Go for it. If you dont like it you can always change it back.