So very true! If the FR is in a sealed (very small volume) and allowed to run FR with the sub being rolled off at 200-300 hz (i perfer sealed again for the woofer) and both are bi amped then you have a very effective system thats a simple build.
Although i am a horn nut , this method is very simple ( to me anyway) as i use gainclones and can wip one up in around one hr.( case not included). Or just put a cap on the front end of one of those little Sonic T amps for the roll off of the woofer and use another for the FR.
There ya have it a cheap/simple effective system that probably would cost < 500$ with a quality FR driver and woofer.

ron