I assume you can buy more sounds for the Nord? I have read up extensively on the Stage 3 but not the piano. Currently making do with a Korg B2 for that.
Anyways, everyone seems to have misread my pianoteq comment as me intending to use a laptop; not the case.
Zynthian is a raspberry Pi project that collects up basically everything Linux has available for music and puts it in a small box suitable for pedalboard, rack, on top of your Nord, etc. It works beautifully and with a hifiberry sound card is the equal of anything, sonically.
It also implements pianoteq as an engine, so with a pianoteq license, it really does do everything the Stage does, minus the keyboard natch, and quite a lot more besides (DSP with stereo in out, mod devices, puredata). So you could have a bunch more piano sounds in a small device that is also a full box of toys for not too much.
They are also weeks/days away from releasing a new hardware version that looks really great, the bdfl has been posting stuff in the discourse.
Things are progressing in Linux, folks. Good times.