i argue the best way to implement a 2 way home stereo is the same as you would a 2 way PA. Get an active crossover, preferably with delay and variable slopes . behringer do a stupidly cheap digital crossover (bout £140) that has 3 ins and 6 outs, i.e. you can go 3 way if you have the cabs.
Ive built both wicked ones and a 12" death box, i think to sound best with a deathbox you should place it between your main stereo speakers, and play around with moving it 20cm forwards or back untill you get the bass and low mid souding together.
My deathbox was loaded with an eminence omega pro 12", ended up having the insert about 2 inches from the bottom of the cab. Sounded good and could be crossed as high as 150 or so. with a poor driver id recoomend crossing it at about 80hz as the cabs less noticable then and gives your stereo speakers more to play with.
dont use a 10 and 12 death box together they will cancel parts of each others response out, you say it sounds louder with one, it will, no ammount of eq-ing, delay or placement will solve this.
go with the 12, cross it at 80-90hz , play with its placement a bit and enjoy. if its still sounding ropey build a wicked one instead
talking of wicked ones if anyones using one at home i reccomend delaying your mid tops (if they are inline with the mouth) about 1.53 meters and crossing at around 85
also if anyones looking for drivers for either a death box or wicked one get the beyma 12"lx60's there nails.