Ever tried putting a cap inline with RCA for XOVER

Hi There, I am trying to cross over my speakers on the cheap.

Anyone ever tried putting a cap inline with an RCA input on a amp to act as a passive High Pass Filter? I am trying to cross over my Wilson Cubs at about 70-80HZ.

My amplifier is a Mark Levinson No. 332 for Reference.

My goal is to build an adapter (Female to male RCA) with a capacitor in there to act as a passive crossover. I know this can be achieved on the interior of an amp but this amp is about as much of a cream puff as youll ever find, Im doing nothing to her (She got completely recapped and upgraded with better parts all around in 09 so shes good for a good long while now)

If that doesnt work how about a good DIY design? Should I go active? I am trying to go not too expensive and potentially avoid another box in my system, but I dont want to degrade my signal greatly, however I do believe a little signal loss would be an ok trade off for less woofer excursion

Which is better, Woofers working hard with more signal or.. working less but a tiny bit less signal?

Oh I play my music loud and listen to electronic music, acoustic is not much of an issue, White Zombie made me realize I was within 75% of the excursion limits at mid volume, I want to be able to play these guys loud and cant hit the high 90DB to 100 or so DB like I want, I am probably chickening out at 90 or so if that.

Thanks

Toby