Ciao,
I have 8000s as well. I'm using an Adcom power amp to drive my old (refoamed) large Advent speakers, circa 1978 (famous for their deep rich bass) set up as as subwoofers. To accomplish this, I bought on EBAY a Dalquist external crossover, which is hooked up between the pre-out jacks from my NAD 3200 pre-amp, and the rca cables running to the 8000s, and to the Adcom power amp. The crossover frequencies in the Dalquist are fixed for the 8000s at 80hz, while the low end cutoff is flexible, from 20 to 200 hertz. The levels fot the subs are variable, so fine tuning is possible. The whole setup sounds amazing. I have the 8000s in front, and the big old Advents behind my couch (though they still look great with their walnut veneers). With the 8000s not having to deal with the low frequencies, they sound even better- 130 watts without the stress of having to cope with sub-80hz. The Advents have amazing punch and depth- they can handle, at very high volume levels, a direct-to-disc vinyl recording of a 6000-pipe organ, with pedal notes reaching down to 32hz (played on a B&O linear tracking turntable, with a Soundsmith mmc1 cartridge). The soundstage, depth, clarity of the whole setup is amazing. The Dalquist crossover cost about 150.00. I'd be willing to bet that my setup sounds better than if I was using a new B&O source... I hope this helps!
James