My comments, forget the rear firing woofer. "Being able to put it close to the wall" is just marketing dept mumbo jumbo. And doing so complicates things unnecessarily. The floor is a far better means to add boundary reinforcement than a rear wall ... distance to the floor is a constant, not a variable and as such can be modeled/simulated accurately. And physically closer to the other drivers makes time/phase integration less problematic. Side firing woofers are done to keep the front baffle narrow, but with some decent woodworking skills you can put a 10-12" woofer on front and still keep your baffle narrow (the best option of all btw).
In short there's no performance based reason to put the woofer on the rear. It's simply done because somebody drew it up that way and the market guys said, yea we can find a way to sell that.
Just adding a woofer the N3 crossover likely won't give satisfying results. You have to add a high-pass for the N3 woofers obviously, and the pass band gain from the woofer will throw off overall balance above the woofer crossover point. To do it right, you'd need to start from scratch or at least tweak the N3 crossover to accomodate. That's if you're talking a full passive network.
If you're talking actively integrating the woofer, that can be done more easily ... but how is it any better than adding a subwoofer? With a separate sub enclosure, you can get phase alignment through physical positioning. With the 'sub' being in the same box and actively crossed, phase alignment takes processing which many solutions don't have. And IMO, the MiniDSP is not a suitable audiophile component. I literally hate mine, it sucks the life out of anything it's hooked too.
I've lost track a bit of what I'm saying, but IMO the best way to go about it is with an all new network for your creation. The Peerless 835017 is a real b*tt kicker woofer that has an extended top end, and high enough sensitivity that it would integrate very well into the N3. But to get the most out of it, you'd want to releive the N3 woofer from having to take care of baffle step losses and let the 835017 do that job ... which means a new network. Dannys woofers are a piece of cake to work with, so it wouldn't be difficult. The tweeter network could likely be left mostly unchanged with just tweaks to the padding resistor for whatever the new sensitivity is.
