Would it might be the FA502 you have on order 🤔
Have that one and it’s great..
Plate amps are not on order. They are on my dining room table. 
But because I’m converting a 2-way passive by adding a subwoofer and amps, the amps are the FA253s. The panel above the amp is where I’ll place 2 pairs of speaker jacks to connect to the speaker on top.
Does the plate amp have to be in the cabinet?
@onhwy61 - That was kind of the goal, but I guess hypothetically you could put it anywhere. The massive reduction of separate electronic components is high on my list of features.
I really like your idea of using the subwoofers as speaker stands, that’s a very efficient and elegant use of available floor space.
Thank you.
Ime in this sort of setup the imaging of the mains is improved by the use of spikes underneath the subs.
Thank you for the suggestion. It’s not shown in the image but the cabinets will have threaded inserts sized for IsoAcoustic Gaia II footers. My modest space will require the cabinets be half on and half off of a rug. Spikes are a PITA on a wooden floor and I’ve had excellent results with IsoAcoustics. I'd rather have something I can push around without scratching the floor. :)
The only other (weird) configuration I can think of that might be worth considering is one woofer down-firing and the other front-firing. Again you’d probably have to shift the plate amp northwards.
My Libra soul’s requirement for symmetry would never allow this to happen. In these dimensions, if I had the energy and money to experiment I’d probably have been well served by using a single floor firing woofer. In the early design phase I had a choice between 1 woofer, ported or 2 sealed based on their volume requirements. I could have done one downward firing woofer. I’d get to ~ 20 Hz with about 84 dB /1W. I really thought a lot about how Snell did it. However! Snell also had long term reliability issues with that setup AND I just don’t have the energy to play with finding the optimal height. While I really love how the Snell A series sounded, I strongly suspect there was more to that downward firing woofer than just mass loading. The size of the cabinet and distance to the floor probably played an enormous part in the success of that speaker. I didn’t want to half ass it without being confident I fully understood the design parameters. 2 forward firing 10" woofers starting from the ground up, crossed at ~150 Hz.... that I understand.
At the end of the day I traded 1 ported for 2 sealed drivers, gaining 6 dB of sensitivity (90 dB/2 watts) with an expected anechoic of ~ 40 Hz. In this room I’ll 100% take it. I suspect the room gain and modes will have me using EQ to reduce the bass, not adding to it. but then, I have to have that perfect measurement profile for JA to review.
How are you going to isolate the speakers from the subwoofers? Are you concerned that the bass vibrations will affect the overall sound?
Well this is a problem for ANY multi-way speaker, so lets keep our concerns in proportion. With the traditional multi-way you would have baffles between the woofer and mid, and share the sides. That’s a lot of contact area to transmit vibration.
One way or another I’ll use isolation under the 2-way speakers on top. The contact surface from the bottom section to the upper will be very small compared to a single monolithic 3-way.
Currently the speakers are using speaker stands from Butcher Block Acoustics. I’ll make some final decisions about isolation when the cabinets are in. I’m sure I can address that, the issue is more about my ear height and where I want the tweeter and mid-woofer to be in relationship. The other real concern, which Duke brought up earlier is making sure your speakers don’t "rock" the wrong way. That the woofers aren’t pushing the speaker back and forth causing a kind of Doppler distortion. You may have seen me suggesting weight son small stand mount speakers to reduce this.
Maybe also help to know that while these drivers are called "subwoofers" due to their ability to play low I’m using them more as a traditional woofer. They’ll cross high but go deep.
Might not make for the most attractive cabinet though...
Exactly. But glad you found something that works for you in shows... those rooms are killer.