Hi Rikki,
Obviously, your question was too hard. Slow response!!!
My comments,for what they are worth, from a juvenile piano player.
My first impressions would be that 73 should be enough for anyone but a concert pianist, but recent posts will give you varying opinions contrary to that.
Relative to console organs with extended keyboard range,with which I am familiar, when compared to spinet organs, with lesser key range, I always found that the spread/quality of sound was always far superior with the extra keys.
i do not profess to know the technical reason for this, but no doubt others will soon respond.
I have also been a longtime fan of piano action keys for expressive playing.

P.S. I am sure your partner is pleased that sports cars were not your hobby !!!

Ray