Well, I had a play through all the Kremsegg instruments last night. The Bechstein is very nice. The only other one that I like is the Erard -- the older they are, the less I like the sound except for the anomaly of the Erard. I'm sure they sound fine in the right hands and with the right music (such as in Phil's excellent YT vid above), but they don't sound nice to my ears or right for my playing.
It's a shame the Kremsegg instruments are bundled together and aren't sold individually, for say €15 a piece. I would definitely buy the Erard and the Bech. I don't think I can justify buying both collections just for those two and I'll think twice about buying KC2 just for the Bechstein.
I suppose if I never used the other historic instruments it'd be no different to buying "just" the Blüthner for the same money, but psychologically that seems like getting a lot for your money (because I like it), whereas buying four and only ever using one (even though I quite like it) seems somehow to be a bit of a waste.
I guess perhaps I only like the sound of modern pianos, but then I loved the late 1890s Bechstein grand I played a few years ago and I adore my own youthful 1903 Bechstein upright (although obviously that's going to sound different).
Ultimately, I'd love Modartt to do a modern (or more modern) Bechstein in the way they did with the Blüthner.
PTQ Std: Blüthner, K2, YC5, Steinway D, Kremsegg 2, Celeste, Hohner, Electric pianos
UbuntuStudio, SL88 Grand, Keystation 88es
1903 Bechstein Model 8, Yamaha CP-30