Anyone Successfully Go from Floor Standers to Bookshelf Monitors w/ Subs?

@OP, lots of recommendations for this speaker or that speaker but to directly address your concerns :

" I am concerned about the ability to fill the room" and
"We don't want to take a backward step but can live with a sideways step"

@spenav mentioned some good points but disagree that room correction is necessary.

Without going into too much theory, know that it is entirely possible to assemble a stand-mount speaker and multi sub setup that will outperform even very expensive and huge floor-standers.

Bass from a pair of floor- standers will never energise a room smoothly simply because the speakers are placed where they can best create an image and sound stage. If the speakers were located where the bass was given priority then for sure there would be no stage or image apparent.

However, when separating duties, the monitors can be easily positioned in the optimum spot for imaging and the subs can be positioned where they integrate seamlessly. It takes 3 or 4 subs to achieve best results. You have 2 subs (from your post?) so get 1 or 2 more. To experiment perhaps borrow a couple of subs, even a pair of 8" subs will do as they are used as tuning devices. With this approach no DSP or room correction is necessary.

I encourage you to read documents and articles by Earl Geddes, Floyd Toole and others on Distributed Bass Array (DBA)

The multi-sub approach and some bass traps optimises bass performance and this really needs to be heard to understand. The peaks in the bass frequencies are reduced and the nulls and partial nulls are filled in some. Nulls, which I am sure you understand, contain no information. It's MIA. EQ and DSP can't manufacture this info.  Going this route is truly transformative and would be no sideways step. Think huge step up with room filling sound, probably better imaging from monitors with a narrower baffle and detail not previously heard.

Moving air is the job of the bass drivers. Sure. Just place them in the right spot.

+1 for Wilson Benesch. Contact: Brian Ackerman at: Aaudio Imports: Contact Us

I'm in the process of just going with standmount speakers.  They are just so easy to move/swap out.  Let's face it, moving spiked floorstanders around in your listening area isn't very fun and I'm tired of asking for help.  Trade off is less bass but you actually get use to it after a while and some of my floorstanders didn't have enough bass anyway.  I have stereo subs but sometimes I don't even turn them on because of what was mentioned above.  

Dear @lemonhaze : For one seat position/sweet spot two true good designed subs are enough.

Regards and enjoy the MUSIC NOT DISTORTIONS,
R.

I went from the following 2 channel system in a very large listening space:

Revel Salon 2 speakers
dCS Puccini Player and Puccini U-Clock
Krell 402e stereo amp
Transparent MM2 Ultra Interconnects & I wire speaker cables
PS Audio power plant AC conditioner

To a much smaller system (speakers) upon down sizing:

-dCS Bartok with headphone amp and dCS Rossini Master Clock
-Dan D’Agostino Progression Stereo amp
-Krell Ultra 4K UHD Foundation Pre/Processor
-Transparent Gen 5 Ultra Interconnects and speaker cables
-PS Audio AC power conditioner
-Evolution Acoustics Micro One stand monitors (these are measured to be at -3dB at 35 Hz)
-2 JL Audio Fathom F110 subwoofers
-Custom, highly modified high-end Mac Mini with high-quality linear, ultra quiet outboard power supply for the music server, running Roon
-High-quality power cables of various brands for all components (MIT, Cardas, Shunyata, AudioQuest, etc.)

I am quite happy with the ‘downsized’ system. To be fair, this system is more expensive than the older one despite the much more expensive speakers (Revel Salon 2’s list for $22K). Of course the digital front end in the new system is better, and all the cables have also been upgraded. The only area of the audio spectrum that was slightly better in the old system 

My view is that the only area in which the older system was superior is the midrange. Not in a dramatic way, but a tiny bit more detail and robustness. I attribute that to the Salon 2’s having a 4.5 inch driver dedicated to the midrange. The Salon 2 is a 4 way six driver system, versus what now is essentially a three way system. In my current system, the mid/bass drivers handle both the midrange and mid bass, down to the 24dB sloped crossover point at 55 Hz. I think the wider bandwidth the mid/bass drivers handle results in just a bit of compromise compared to the dedicated midrange driver. One other thing that is not an issue for me—the standmounts will start to compress a bit at very high volumes, well before the Salin 2’s do. However, I don’t listen at those volume levels anymore.

Other than that, I would say both the high-end and bottom end are certainly better in my newer, smaller system, and that it is superior overall to the older system. Some of that is due to the superior digital front end and upgraded cabling throughout the system. There is no doubt that as good as the bass is in the case of the Salon is, even with an amp like the Evo 402e (400/800/1600 very high quality watts per channel into 8/4/2 ohm loads—the Salon 2’s require this type of power to shine in a large room), the 2 JL Audio Fathom F110’s are simply, easily better. My Progression Stereo amp is also quite powerful, 300/600/1200 watts into 8/4/2 ohm loads, which is more than adequate in my room. It is also a bit better amp due to newer, better design and superior parts, and should be since it is $4K more than the Evo 402e was. Furthermore, my current system is very well balanced with regard to matching the subs and the stand monitors due to a combination of factors—the Krell Foundation Pre/Processor and the subs both are amazingly good at matching things up in a system like this. DSP technology along with an included microphone in both cases automatically matches each speaker (in my case, a hybrid 2.1/5.1 system) in terms of ensuring that the signal from the stand mounted monitors reaches the sweet spot at exactly the same time as that produced by the woofers, center speaker and rear speakers. This is the case in both 2.1 channel and 5.1 channel modes. The Krell also allows one to pick both the crossover point and slope (12 or 24 dB/octave), and vary the volume level of the subs on the fly easily via the remote. This a fantastic feature you won’t get in a ‘fixed’ speaker system like the Salon 2. It’s great to be able to either augment or reduce the bass according to the recording—some have too much bass, some have too little, and this capability makes the system much more satisfying to me, as recordings that are too full or too lean on bottom end are quickly and easily adjusted for a much more satisfying experience.

Final note—I am getting ready to upgrade the EA Micro Ones to Magico A1’s. After that I intend to upgrade the interconnects and speaker cables to either Transparent Reference or XL levels, and upgrade from the dCS Bartok with headphone amp, likely to a dCS Rossini DAC (will keep my Rossini Clock).

Hope this long post helps—one can certainly do very well with a system consisting of high quality stand mounted speakers and high-quality subs. One important note—I believe the best route is with smaller, very high-end subs like the JL Audio Fathom F110’s I have. These 10 inch subs are faster than the larger alternatives, and therefore blend/match better with the mid/bass drivers in the standmounts than larger subwoofers. They are quite compact as well. A pair does a phenomenal job in a room that is large, but not huge (mine is an open living area that has an 18’ ceiling, is 32’ long by 19’ wide.