Cork, you have 2500 sq ft to fill and it's open to that much more. No sub means you need linearity down low so you don't get booming or nulls. You also need to get down to 30Hz or so to cover the jazz, classical and classic rock. So let's look at the options carefully.
The only traditional Axiom speakers that will get down that low with some room gain are the M50, M5, M60, M80 and M100. The M80 and M100 reach a little lower than all others.
The M50 has no mid-woofer and that makes the mids sound less detailed. But they are very enjoyable. What makes them terrific is they can be dropped in any room and there's no booming - but the nice bass is there! The bass is very linear and they go loud. If I couldn't use a sub or EQ, I'd take the M50 over all others except the M60.
The M5 gives you the detail the M50 is missing. But they're not as linear as the M50 down low. They boom in my living room and still need EQ in my main room. They may work in your room with careful placement and maybe port plugs and EQ. I say maybe to port plugs because I find the port plugs affect mids in a not good way. Maybe though you won't object to them. And they're not the floor-standers you worked so hard for.
I haven't heard the M60. But it looks as linear as the M50 and it has a dedicated mid-woofer to boot. I bet it can be dropped in any room and it will sound very nice.
The M80 is a bit of a curvy ride down there. It's a crap shoot what that will sound like in your room.
The M100 is better. In a room that size, and a 14 foot MLP, the 100 is a good fit. You may have to experiment with port plugs and placement to get nice bass. I admit I could not get nice bass out of the M100s in my 1900 cu ft living room or 4200 cu ft main room. I had to use Audyssey XT32. They sound much better in my buddy's 6500 cu ft space.
That brings us to actives. The 880 will get you down that low better than the 660. And it appears all the linearity challenges Axiom has with the 80 were erased with the DSP. Awesome! But the 660 is close and with room gain, it may turn out to be more linear than the 880. This is why I would choose the 660 over the 880.
Now I'll also tell you this and it may or may not be a big factor for you. For me, it's a big deal! The M2, M3, M5, M50 acoustically disappear. I could not get the M80 or M100 to do that. Maybe if you're seating in the near-field and they're 12 feet apart (like CanesinVirginia) they disappear. Maybe at your 8 feet apart and 14 foot diffuse field MLP they'll disappear. I don't know. Why don't the M80 and M100 disappear as well? Because multiple mids and tweeters are difficult to perfectly integrate. But they'll go louder with less distortion. There are trade-offs.
If I had to go passives, I'd go M60. I'd get linear bass, wonderful fidelity across the board and I bet they disappear, due to a single mid and tweeter, leaving me with just soundstage and images.
If you don't want trade-offs, the active LFR1100 has totally linear bass right down to 28Hz in room, and completely disappears and has deep, wide soundstage with the best imaging. You get what you pay for.
