Bi-Amp Woofers with Class D?

Bi-amp, horizontal. Haven't used class D on anything above 100Hz, but you could use your integrated for the mid and highs if it's separable with an electronic crossover. Been bi and tri-amping for 42 years, not going back to passives any time soon.

I do the same I use a passive XO 250-280 hz and up. 280-300hz and down it's an active crossover with full blown correction.

I use 12K class Ds. Bullet proof & a 2496 active crossover. I can't break one.. 3500 watts @ 4 ohm per channel.  They can do 1 ohm but 2 ohm stable for a while.. :-) 500.00 with volume control.

OXO (2496) is about 300.00 or so.. + 100.00 or so for # 10 Cables, speaker and PC

I run 6/12 8" MB drivers in two 42/76" columns. Clear as a bell direct coupled, no crossover between the amp and the drivers. Perfect bass control. Under 1K for everything

You could power 2-12 12" HE drivers very easy.. They run so cool I disconnect 2 of the 3 fans and use a mini toggle switch for the one over the power supply. I've yet to turn it on in 3 years. Barely warm to the touch when I'm blastin'

Regards

Works good.

My speakers are full range to 20Hz but because there are standing waves in the room, no bass at the listening chair. I installed 2 extra subs, asymmetrically placed in the room, to break up the standing waves. They are driven by a class D amp that is rolled off above 60Hz. Now the bass at the listening position is correct like it is elsewhere in the room.

class D offers tons of power for not a lot of space and not a lot of dollars. 
pretty good for freq below 80 hz. And if you buy a class D amp to drive your woofers, go get a big one, not something intermediate....

what is the configuration of your speakers? 

Avanti,
Wish I could post a picture. I use an equilateral triangle arrangement overall.
The speakers in the FSMs consist of a 15" coaxial and a 15"woofer
in each unit. 
Is this your question?

Atma,
I am starting to think that rather than bi-amping I should consider
buying two REL T7 powered subs.

Any thoughts on that?

I am starting to think that rather than bi-amping I should consider
buying two REL T7 powered subs.

I don't bi-amp; my front speakers go flat down to 20Hz. I use the two subs to break up the standing waves in the room.