Another compromise you could consider is going with a lesser laptop with an SSD and downsizing your library using some kind of auto-resampler like Nuance or Bliss. I haven't personally done this, but have considered it.
It would be a drop in fidelity, but I'm not sure you'd miss it in a live setting. My personal feeling is that I'd rather sacrifice a bit of quality to avoid pushing my machine to its limits all the time. But
Jim Roseberry
If you're wanting to play advanced sample-libraries (with zero glitches ever) using an ASIO buffer size of 64-samples (or lower), be careful with your selection of laptop. Most are not up to this task (even with M.2 Ultra SSD).
If you don't mind playing samples at a 128 or 256 sample ASIO buffer size, many laptops will suffice.
Just one more wrinkle I'd add to this, which perhaps you've already considered; your choice of audio interface can also be critical here, as driver quality/configurability can have a large impact at lower buffers. When I switched from an (admittedly outdated) focusrite to one of the newest-gen MOTU boxes, I had a massive latency improvement even at identical buffer settings, and can set it as high as 512 without being bugged by the latency. YMMV, of course.
Great, more things to research, right? :)