What are the best loudspeakers under $4000 to re-create lifelike piano

If you’re willing to bust the budget (big time) and live with a limited selection of recordings, there’s a "right answer" here:

The diskclavier system, which retrofits to a piano. Effectively, you get a disc-driven player piano. I think the system is owned by Yamaha, but it can be retrofitted to other brands. New Disklavier uprights from Yamaha IIRC start at about $11k or so. A small Grand is closer to $20k. My local piano store has a small, second-hand Kawai Grand with Disklavier available for $12k. That set-up, with or without a disc inserted, sounds (and plays) great.

Im pretty confident that a used Disklavier acoustic piano will get the best recorded piano sound you can find at +/- $10k.

If you really want to stick to traditional-ish loudspeakers, I’d go for powered ATCs. I’ve used them with a Roland digital piano and the sound is pretty damn convincing to my ear. To be clear, I typically use Yamaha powered monitors (very good sounding, themselves) for this purpose (cost considerations), but - several years back - I had a pair in my studio to audition because a friend was selling them. They’re really good, IMO.

BTW, I also play back recordings that I’ve made of the Roland into my DAW (using a variety of virtual pianos, but not the Roland’s internal sound engine) via an Ohm 100/Rhythmik Subwoofer system that is digitally crossed and corrrected with Audyssey. It’s quite a different sound than I get from ATC monitors straight out of the Roland, but it’s very satisfying in its own right.

One more note, plus caveat.

One poster was dismissive of digital piano recordings. I disagree. The odds of getting a good result are vastly higher with digital recording, IMO. My home studio isn’t set up for an acoustic piano, but I’ve been to commercial recording sessions where we made an analog recoding of an acoustic piano. It’s not easy to get it "right" and there can be a ton of debate as to what "right" actually is.

I routinely get excellent results recording a piano in my home studio, using piano-teq modeled pianos, and Ivory or NI sampled pianos. The very best SQ piano recordings may be analog sessions with a great instrument, a great space, and a recording team vastly more skilled than I am, but - on average - digital recordings are preferable to me.

Caveat: My sensitivities to flaws in a recording aren’t necessarily the same as anyone else’s. A squeak from a bench can (and has) ruin an otherwise beautifully recorded passage.

@martykl - not sure if you were referring to my earlier post about the Nord not sounding like a real piano (or a Rhodes for that matter). Just to be clear if you were referring to my post, I wasn't talking about the recording process, digital v analog, but the instrument itself. Yet, at least live, I've heard some electronic keyboards that do a pretty impressive job of emulating an acoustic piano. 
On the history of pianos, those old "reproducing pianos" (which were more sophisticated than a plain 'ole player piano) could let you hear Gershwin playing his compositions. Crazy. Apparently, some (or all?) have been ported over to the Disclavier. 

I love the sound of the piano that my Harbeth C7ES3s produce.  Very natural and life like depending on the quality of the recording  and source of course. 
Joni Mitchell records sound amazing, as does the David Bowie "Alladin Sane" album.  So do certain Bill Evans, Oscar Petersen and Thelonious Monk recordings among others.  The Harbeths can deliver like no other speaker I have owned.  

@whart

I have the latest Nord 5. Like anthing it does some emulation better than others. If you go to the online library you can fine tune. For Rhodes emulation I prefer the Korg SV-1. The Korg SV-1 doesnt do piano as well as the Nord but it does Rhodes well and it has a weighted keyboard for a better piano like playing feel (my Nord is best suited to Organ with its waterfall keyboard) and organ drawbars)

I plug the Korg SV-1 midi out into the Nord and the Nord produces the piano emulation, mellotron, farfisa and other sounds I need. The Korg does a great Oberheim too.

In the end I settled on these two keyboards for the majority of needs. The split function allows me to use both keyboards sumultaneously for different instruments. Neither the Korg nor the Nord do everything well but together it is like Jack Spratt and his wife - got most everything covered to a very high level of authenticity. Short of buying and servicing all the original instruments - i would need a dozen or more keyboards - I find this solution superb.

I am not sure what Nord you have tried but there has been significant improvements over the years. Also the speakers you choose to connect to tbe keyboard are critical - Genelec 8020 are very good for the nearfield sound of the listener while a keyboard amp is necessary to achieve high volumes in a band setting where you compete against drums and guitar.

This is Benmount Tench setup
http://fohonline.com/images/stories/16/07/current-foh/mudcrutch/tech-miking-shots/MUDCRUTCH%20BENMON...