From the way I understand it (maybe Gonk will corret me), if the Fonts are set to Large and the Sub it set to L/R+Sub, then all the bass is sent to the front speakers (regardless of that the crossover it set at) and some bass is also sent to the sub. This was the setting that I have used in my system for the past two years.

Now that I have upgraded to the newer firmware, I found that I was getting way too much bass. To correct this, I changed the Fronts to Small with a crossover at 40Hz and the Sub is set to Yes. That way the front speakers only get bass down to 40Hz, and everything lower than 40Hz is sent to the sub. I tried setting at 60 and 80Hz, but 40Hz sounded best, since I'm using florstanding speakers that can go down to 40Hz.