Higher Efficiency Speakers

I am going to start my quest for speakers. My room is 13.5x13.5 but open on two sides... so not an ideal space. But never the less this is what I have to deal with.  I have a set of Vandersteen 2ce Sig ii but would like to upgrade. Was thinking about something horn. But seems when you go that route it gets way out of my price range.  Thought maybe look around for some Used Vandersteen Quattro CT but budget starts to stretch at that point. Like to stay under $10,000. What would be good speakers to look for to demo? If my room was alittle bigger.  I’d almost go the other way, and look at Small Maggie’s and Monostrap my amps.
Atma-sphere M60
Atma-sphere UV-1 ( Probably the most Modded. Will be at the end of the month. Lol) 
Bel Canto Dac

  If you are worried about your listening room, call Spatial Audio. I do not have an ideal room, needed high eff. speakers for a First Watt J2. I went from Tekton (which were very good speakers) to M3 Turbo S, then upgraded to the Triode Masters. Very satisfied, they are worth a phone call.
I tried Zu's and though they were good, they weren't as good as Vandy's.
Maggie's with a Zero Autoformer might work with the M-60-Once again, Ralph would know. He does speak highly of Sound Lab speakers.
Earlier in this trail somebody suggested having 100 dB efficiency speakers would give a freedom to chose from a wide range of amps. I did just that and am now running 1W/channel (yes, 1W) Linear Tube Amp called microZOTL2 with Teresonic Integrum speakers (104 dB) and get the most satisfying sound I ever had. The amp uses signal tubes only and pure class A with amazing results. Teresonic's on the other hand, with no-crossover design create a dynamic range that has to be heard to be believed. Yes, high efficiency speakers will take you places were others can't even think of.
Hi pstores, I had the same Vandersteens you have, as well as KEF 105 Reference 2s, Thiel CS-7s, B&W Matrix 2's, and upgraded the caps and resistors in line with the audio path in all but the CS-7s, because before I got around to the CS-7 crossovers I bought some Audio Nirvana AN15 Alonco Classic full range drivers. I purchased a DS2 preamp from Don Sachs, and so I knew that he knew his audio, and he recommended them. David Dicks, the owner of Audio Nirvana, almost convinced me that he was completely full of it because of the old addage that if it sounds too good to be true, it probably isn't. I had inexpensive unfinished cabinets made so that they were done before the drivers arrived as I was pretty confident that I would be returning them. Once they arrived, while over all they didn't sound that good, the vocals immediately blew me away. I ran them 24 x 7 until I had well over 100 hours on them, and they certainly needed it! They began sounding pretty good, better than anything I have ever had in my system, even better than the Quad 57's which I loved, but they had no volume, no bass, and like all the Acoustats that followed them, compressed dynamics. None the less, what the Quads got right made them some of the most musical speakers that I had ever owned, but I couldn't live with their limitations. Anyway, these sound better than the Quads. I had no idea how badly even a crossover with the best components suck. David offers a 30 day return policy, so get the enclosures made first, and use SS gear so you can drive them for at least 100 hours before taking them seriously. After that, using your best gear, give them a reasonable serious listen. They'll continue to improve, though after 500 hours or so I am not sure that you'll really notice much more improvement, but allegedly the more you play them the better they sound indefinitely, but I can't speak to that. I can say that to better them you'd have to spend a boat load of money. I used V-Caps, and or Mundorf Silver Gold capacitors to bypass the crossover caps in my speakers, so I was getting about as much as could be gotten through the crossovers, but some very good speakers were embarrassed by the AN speakers. They do have detractors, but I have no issues with them whatsoever. For under 2K, if you go for nice cabinets, they are the best sounding speakers I have ever heard.
There are multiple choices in the Tekton line that would check off on all your boxes......big time.