the polk rti 100s are specd at 25Hz-27kHz. so no you would not be losing any bass that is going to the surrounds unless it is under 25Hz. i have not seen a movie yet with a surround track dipping that low in frequency anyway.

conversely you would be gaining all of the mid-low bass from your surrounds rather than from the sub, which could be dedicated only to lfe. i like my setup to have full range everywhere with that channel's bass being handled by the appropriate speaker and the sub getting only the signal it is supposed to get, rather than the lfe + the crossed over bass from all the other channels...

those settings are not for everyone, but if you have all large speakers it is best. i guess MOST people dont have full range surrounds, so that is why the crossover settings come into play a great deal for them as far as tweaking the sounds...