You're right. The 630 works the same way -- I was working from memory and mixed up the "Sub" and "LFE" settings. There does not seem to be any way to accidentally stop LFE content from going to the sub except by setting it to "None".
The interesting thing is that the 630 seems to let you send LF content from the mains to the sub even though the mains are set to "Large", but does not offer the same capability for the Center channel -- ie if you set Center to "large" then there is no center channel content going to the sub. Not sure why mains are treated differently (maybe for stereo ?)... but until reading posts in this thread I had always assumed that center speakers would always be "small" anyways.
The crossover treatment for the LFE channel is interesting. LFE can be low-pass filtered, but it shares a filter with one of the other speaker channels (ie you pick L+R or Center or Surround etc... and it uses the same crossover frequency as those speakers). This explains a lot, and tells me that I probably have some really stupid settings today and am losing some LFE content as a result.
None of this explains why running "Large" on the center channel gave Misfit Toy clearer dialog. I also don't understand why a deep bass slam would be encoded onto only the center channel and not onto LFE. I guess if either of those two changed then Misfit Toy would be happy again
