$15,000 Floor-Standing Speaker Selection and Advice

I have a great room about the same size. You don't necessarily need towers. So much depends on treatment effects of carpet, upholstered furniture, wall decorations and window treatments. Furniture placement for listening matters. If you don't go with a tower, then a sub is recommended. I use a pair of JBL 4349s and with a not-especially overpowering group of amps, usually an Audio Research i/50 or a Sugden A21 SE Signature. I also have an alternate system of Amphion Argon 3s standmounts with a ProJect digital Preamp and a NAD C298 Purify amp and a REL sub (using the Arrow wireless connect.) You really don't need an overly-large speaker or amp. If I were  looking to reduce footprint, the Buchardt A700s and a DAC-preamp  like the ProJect PreBox RS2 Digital or a T+A DAC200 might do well.

@chenry By the time you buy good quality subwoofers, two or three plus good quality bookshelf speakers you could have bought floor-standing speakers with good bass output for the same price. Bookshelf speakers has no appeal to me.

Whether to use a sub or not isn’t entirely a "bookshelf -yes or floorstander-no" choice.

For me in my room, the bookshelf units benefit by having sub reinforcement. The JBLs don’t require a sub.

Fortunately, Amphion also offers the Argon 3LS and 7LS floorstanders.

Standmounts have their advantages. They are certainly easier to move, and for some, that is a factor in choosing.

The OP listed a $15K budget. Some of the replies have a somewhat elastic notion of a "budget."

OP has decided on towers for his space. He lives in OZ, so suggestions of products readily available there might be useful, considering the prohibitive costs of both air and ocean freight. Products made in North America but not distributed in Australia would be inconvenient to access and service, and difficult to audition. All the same, there are many products available there that are similarly not well distributed in the USA.

I suggested Amphion on my own familiarity with the Argon 3s (6 years with mine). I happen to think they punch well above their weight for a standmount, which also many reviewers have written. They make three different floorstanders and are available in the AUS east coast major cities (sorry Perth, sorry Adelaide.)

I also have a pair of Buchardt actives. (The OP listed the A700, Buchardt’s active floorstander.) Mine are standmount A500 special edition with Purifi drivers. Buchardt’s direct sales model uses in-country agents to receive, and all shipping, and duties are price-inclusive. There are also rights of return. I know some are wary of actives, thinking with individual amplifiers per each transducer there is more to go wrong. That really isn’t appearing to be a problem with that company, apparently, but they also make passive speakers. FWIW, I never hear the same case made about ATCs actives. Their passives are close to budget for the OP, and they make large standmounts and towers. Maybe that works for the OP. The suggestion of the TOTL Yamahas is an interesting one, and I suspect that their audiophile products are at least as available in Australia as in North America.

Speaking only for myself, I would not buy any $15K pair of speakers without an audition in my listening space and with right of return for any reason. I certainly would not buy any speaker, new or used, at that price point from an overseas seller that had no service agency in my own country. Now I have bought many of the components online and un-auditioned, but I had purchaser protections.

(People suggesting Avantgarde Unos, for Pete’s sake, difficult to find anywhere, including Germany.)

IMO, a sensible discipline in choosing is to audition what you can that is reasonably available at your price point, select the best speaker found, and then only accept a compelling case for buying anything else.

@hifiworld2024

Lighten up, Francis. No need to be shouty.

Read what I wrote. I get you don’t like or want "bookshelf" speakers. I didn’t suggest you should. I did suggest you look at floorstanders made by companies whose standmounts I am familiar with. You actually listed one of them in your original post, the Buchardt A700s.  And I’m not sure who the "they" is you say offer a free in-home "trail" but if it is Buchardt, I am aware they do, since I bought a pair of their actives on those terms.

You might also look at ATC, the SCM50PSLT passives or the SCM50ASLT actives. They are the floor-standing variant of their large classic stand-mounts (low stands). The passives are a little above your $15K new, but used, probably below. They have the same speaker as an active for more money, as you would expect, but the amplifier match to the speaker is good.