Starting from scratch in a large room

Certainly the 24" deep shelf is your best option for larger (deeper) speakers than in bookshelves. Not too deep, some toe-in will be needed.

What height is that shelf? Generally you want your tweeters at seated ear height.

A bit further back than an iso triangle works better for many, so: a few feet from side walls, 18 ft wide room, speakers perhaps 12’ apart, 15’ even18’ back should allow decent l/c/r imaging. against rear wall, probably no real depth imaging.

You could start with your all in one amp, and then some smaller inexpensive speakers intended for a second system later. ’Learn’ the room, mess with locations, heights, toe-ins. After gained knowledge (researching ’real’ speakers all the time), then more informed choices can be tried.

Nothing wrong with a moderately priced set of speakers and better speakers a few years later either. We all have ’moved up’ over the years.

IF buying an amp first, consider ’extra’ power now IN CASE you might want to try some inefficient speakers (low sensitivity, below 90 db/1w/1m).

Real bookcase speakers are no more than 12" deep, have no ports, and can be used horizontally.

I have re-discovered and reconditioned Vintage AR-2ax, 3 way ’real’ bookshelf speakers, 11-1/2" deep 13 high, 24 wide, 10" woofer, with level controls to adjust output of the mid and tweeter relative to the woofer ’in the space’ to get the best frequency balance in any given space.

Originally purchased for nostalgia reason, Intended for garage/shop, sound soooo good I kept them in my office and bought a 2nd pair for the garage/shop.

I have tools, experience, skills to rehab them successfully, not everyone can do that.

compact with 10" is unusual, and level controls few and far between these days. Perhaps make sure your all in one has balance and tone controls.

Others: Modern speakers that offer similar performance and features???

simple 'speakers against the wall' search

https://www.google.com/search?q=speakers+intended+for+against+the+wall&rlz=1C1CHBF_enUS1025US1025&oq=speakers+intended+for+against+the+wall&aqs=chrome..69i57j33i160j33i299l2.12567j1j7&sourceid=chrome&ie=UTF-8

You can build 'virtual' systems on the site here. You could post photos of the room, Copy of floor plan if available or if you can sketch on some grid paper.

here's a link to my virtual systems to give you an idea how they work.

top of page it says 'create system'.

36" shelf is a good height for horizontal speakers, beams drivers close to seated ear level. (42-48 for me, I’m tall, depends on chair height). Typically tweeters toward the center, keeping their narrow distribution more toward the center.

you can add something below as needed

btw, toe in. you can keep them ’straight’ for casual listening, toe-in some for 1 centered listener, toe them in more for two listeners, back to straight for wife factor if an issue. consider an appropriate amount of material that permits movement yet allows them to ’feel’ heavy on the shelf which hopefully is solid.

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’extra power’.

Usually I recommend efficient speakers, horn type the most efficient, (high 90’s, some over 100 db/1w/1m).

specifically to minimize the amount of power needed, especially if tube amp(s) might be desired now or in the future.

efficient speakers keep cost/size/heat down and increase placement options, consider remote beam and visible line of sight.

horn speakers enclosures, especially unvented ones are large, cubic feet determines amount of bass. (your location precludes rear/side/bottom ports, perhaps front port).

smaller, un-ported, usually efficiency drops, and often impedance drops, i.e. 6 ohms nominal, even 4 ohms nominal. there are some great sounding in-efficent/low ohm speakers, soooo to keep your options open for a large space such as yours, I will relate a recent experience:

friend, large space: 29 feet wide, 45 ft long, high ceilings.

JSE Infinite Slope Model II’s, sensitivity 91 I think, fairly easy load.

McIntosh AMP, MA2270, 270 wpc, BIG Meters.

Playing decently loud: typical 2.7 watts used; frequent 27 watts drawn; occasional 200 wpc; and infrequently but repeatedly the Power Guard came on, indicating the amp was preventing clipping exceeding rated 270 wpc.

Of course you can drive any 91 sensitivity with an 80 wpc amp, however, dynamics in content will need more instantaneous power. Size of space, desired volume, music dynamics are all involved.

So ’extra’? More power is not linear. IF I recall correctly: For each +3db in loudness (a perceivable difference) DOUBLE the power is needed. So a 150 wpc seems like a lot more than 80wpc, and yet ....

Restricting yourself to efficient speakers is wise, they get bigger, especially not ported, what is the wife factor for big speakers horizontal on a shelf?

Consider limiting yourself to a stereo amp that can be used MONO, so you could always buy a second one in the future.