The Best of the English Sound

Just to throw you on a whole different possible tangent; I was listening to small monitors (nothing extraordinary, but very good ones) in my desktop/computer/workstation system. I found it a bit distracting for some reason and I suspect it had something to do with a narrower sweet spot. I switched over to Ohm Micro Walsh shorts, which are omnidirectional speakers. I really love the vast soundstage that seems to remain unchanged no matter where I position myself at the monitor. I don't know how they'd work in your setup - I took a peak at your system (nice integration into a living space, and major WAF runaround going on there...well done!). You're listening in a very open space in nearfield when you sit at your monitor (listening to the workstation speakers), whereas I'm in a much more confined, tighter, closed space...a small basement office. Naturally, YMMV, but it's a thought anyway. I've only once heard ATC at the house of an audio engineer in his personal system. I've heard Harbeth perhaps more frequently, both at a friend's listening room and at shows. For whatever that's worth, Harbeth occurs to me as one of the most relaxed, laid back presentations I've heard, whereas the ATC's I heard were far more forward, almost to the point of aggressively so. ATC's seemed more neutral, while Harbeth's seemed to add just a touch of coloration towards warmth and were utterly non-fatiguing. They were not my taste - I prefer a more forward sound - but I certainly appreciated what they did well. I would say they are very different presentations. The ATC's were larger than what you are considering though...I believe they were the 20's. Harbeths have been various sizes (always occurring to me to have a similar presentation), but my friends were 7's (about the same size as the ATC 20's I think, but not desktop material). I'm sure folks with more exposure than me can lend more authoritative observations. The one thing that always sticks with me with the Harbeths is how laid back they sound (as in a recessed soundstage).

Jax
Looking at Spendor/Harbeth for a desktop set-up could run into some serious money. If you want to try the "British" sound how about a pair of KEF Monitors like the 101 or 102's?
They pop up often and always sell. Price is reflective of condition.
As for the other 2-4 sets for various locations there are
bookshelf,stand mount,floostanders and others to consider.
People either like or dislike the British sound. Once you get bit by the mid range and the sound of vocals,you too will be a believer! You can listen for hours and rediscover
your whole music collection.
There is a ton of history on the designs of these speakers,
most having to do with the BBC.
Also, Spendor has had a monster sized price increase so used is the way to go. Good Luck & Happy Listening.

Get Wharfedale Diamond 9.1s. Currently on Amazon direct from the company for $269. They are quite small but have had excellent reviews in the British press. I currently have 8 pairs of British speakers myself and would get a pair except that my wife would kill me. I have been both a Spendor and a Harbeth dealer, as well as B&W, Leak, Musical Fidelity etc. so I like the British sound myself.