Hey bob,
The BFD should be inline between your receiver or pre-pro and your sub amp. The sub pre-out is adjusted to achieve the proper input level in Bypass mode. Then you set your volume on your sub to level match with your mains.
Couple mode is pressing both engine buttons simultaneously. To make sure they are uncoupled I beleive you would do the same. Then to use each engine independently simply press the left engine button and then the right engine button, turning both on independently. But I'm not 100% sure this is correct on the 2496. I think this is something that is actually pretty well explained in the manual though.
Most everything will be the same on that unit, except you will get more filters per channel.... BUT you lose any extra presets as there is only one preset per channel. Okay... you would have saved a few bucks too. I know... just pile it on.
