You may want to give Outlaw a call and talk this over with Scott -- he should be able to answer all of your questions, but the Outlaws do not generally post here in the forum. I can offer some thoughts, but I may be misunderstanding some of what you're doing. Having said that...

Enhanced bass sounds like what folks around here have been calling "double bass" -- full range signal to the mains, but low freq information from the mains also sent to the sub. This does sound somewhat similar to the "L/R recombine" option on the ICBM, although that is primarily intended for use without a sub. I would tend to recommend using the enhanced bass only if you prefer the sound, but I'd start out with it disabled on the pre/pro -- the central idea behind the ICBM is shifting all bass management to it. The sub input on the ICBM is there because the ICBM needs to get the LFE signal (the separate ".1" track, independent of the five or more full-range speaker tracks). The ICBM does the rest. I don't know why there would be distortion or anything from using the enhanced bass in conjunction with the ICBM, if you chose to use it.

What pre/pro are you using? I'm wondering about the filter frequency option that appears when you have the sub on -- in some cases, a unit's setup will still have the option of setting a crossover frequency even when it is not actually used, such as when speakers are set to large. (For example, Outlaw's Model 950 has separate crossover points for the mains, center, and surrounds -- you can set these to anything you want, but if the associated speakers are set to large the crossover point is ignored.)

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