IMO, it is counter to the whole design and advantages of single, full-range drivers to put any extra electronics in the path, especially in the speaker signal. You are adding a capacitor at a minimum. Active crossover (in the low level signal) is less damaging, but still sucks some life. If I understand your meaning correctly, the passive hi-pass filter you mention is just half of a two-way crossover. The effect on the sub would be eliminated (where it doesn't matter so much), but the same filtering for the mains would exist as a full xover.
I've been through it all. I had a high quality active crossover from Marchand splitting the signal for awhile. I've since gone without it and the results are much more clean and dynamic. Subs will blend just fine with some tweaking if they have any flexibility in controls at all.