Originally Posted by miimura
Anybody know a reason why this isn't a good idea?
It depends upon your crossover setting. What crossover setting do you use, miimura? If it's too high, you'll get redundant bass info coming from both the LARGE fronts and the subwoofer, as pbarach points out. However, if you set the crossover low enough, the redundancy can be significantly reduced, but this is really not too much different from setting the fronts to SMALL and using a low crossover. The problem with using a low crossover in either instance with, for example, XQ1s and an XQ2c, is that it may be too low for those speakers.
In the end, you should use the setting you prefer. For some, the "Max", "LFE+Main", "LFE Plus", etc.. setting may work well. For others it may not.