Funny, I was just wondering the same and came away a bit surprised. A quick Google search turned up just a handful of offerings, none of which seemed too interesting. Besides the free libraries from Yamaha ("Montage Expanded" and "Chick's Mark V"), it appears that Motif XS/XF libraries are mostly what's available (which you have to convert to Montage-format). I did find this Yamaha MusicSoft online store with 17 Montage sample and performance libraries (including the free ones from Yamaha) here.

Though there are a few KApro libraries for Montage in the MusicSoft site, I didn't see any KApro orchestral libraries. KApro makes a ton of excellent-sounding EXs orchestral libraries for Korg machines, but I don't see that they produced any of them for either the Motif or the Montage.

There is a "Complete Orchestra" library made specifically for the Motif XF here by a company called DCF Productions. But for just $99, I'm not sure how well it compares to KApro's $399-$799 EXs orchestral libraries for the Korg Kronos, or Orchestral Tools' $2,700 Metropolis Ark I, II, III symphonic VST libraries for Kontakt.

. . . I just listened to some of the Complete Orchestra online MP3 demos, and the DCP library actually sounds decent, and for only $99, seems like a good bargain.

Thanks for your reply. I researched and to a lesser extent made the same discovery. Surprising is putting it mildly considering this is Yamaha's flagship board regarding the lack of sound development for the Montage by 3rd party companies. Why we need so many more FM and Rhodes sounds I'll never know. I just wish someone would design non-vibrato and quick response strings horns woodwinds, tight bigband mixes etc, as what can be found with K-Pro and Korg. I just sold my Kronos 2 61 for various unsatisfying reasons after being a Korg man since the 80's.
Also, thanks for the motif Complete Orchestra suggestion. You are correct for the money, although it would be nice to have something over-the-top for the new board with it's expanded storage capabilities and advanced technology over the Motif.
Still hoping someone out there either knows of or will recognize the need for the non-vibrato etc orchestrals considering the need for this board is to be taken more seriously by pros in the field without going laptop. SOS...
cheers,

Since I'm considering getting NI's Komplete Kontrol S61 Mk2 controller, I'm looking at Cinematic Studio Series' Studio Strings ($399) and their Studio Solo Strings ($299) libraries for Kontakt. It's a medium-expensive sound set that sounds extremely good for the money (the solo-cello is excellent!). Plus, they're NKS-enabled so they should work with the NI keyboard; though, they don't explicitly indicate whether they support NI's "pre-hear" auto-auditioning feature.

The top of the heap I think is Orchestral Tools' Metropolis Ark I, II, III libraries for Kontakt (the Taiko drums in Ark III sound amazing!), plus their two solo sets for violin and cello—very impressive! These total about $2,700, but sound excellent and have a terrific articulation and mic-placement UI. It's too bad you sold your Kronos since the KApro EXs libraries and the Cinematic Suite EXs library I chose from WavesArt both represent the best-sounding strings I think you'll ever hear from a hardware synth. Now, I don't use any of the stock Kronos strings or brass unless I'm specifically looking for fake-sounding strings and brass!

As I learn more about the Montage, it's as if you need either another workstation and/or a full-fledged DAW to meet all of your needs. As someone else put it, Korg's Kronos is the best workstation currently on the market, and the Montage (which is no longer marketed as a "workstation"), the best live instrument on the market.

Perhaps you could get by for now with the $99 Complete Orchestra library, and some time in the future, invest in a decent software orchestral library, for which there are many quality offerings to choose. You almost can't lose with any of the software orchestra libraries, since the samples are so much larger than any hardware workstation can accommodate.

You are spot on with the difference between the two boards. It's a trade-off both ways. I am a heavily working live player and prefer not to use soft-synths/laptop for various practical reasons. Also, not a fan of KARMA. Just trying to set the ADSR in the Kronos was absurd as almost every sound engine of the 9 has a different method. Much of my work demands on-the-fly editing which is why I was a Korg man for so long. I had every major board since the Poly-VI. The Montage is closer to the Triton in ease of programming than the Kronos. I was all over it in less than a week and two weeks later had it's debut in 3 major shows...user friendly.
That said, I am hoping the April release of Sample-Robot for the Montage announced at NAMM will give me some expeditious processing of sounds at least from other keyboards I have access to. I'm ordering the the Complete Orchestra to squeeze out some variety against the stock sounds for now.
I am hoping further development will produce more practical sounds. I am appreciative of your input and understanding, and am open to any other Motif sounds for now you might suggest as I was not a Yamaha guy till now. I do need expand asap.
cheers