spice market, alta, or del posto enoteca
Are any of these good choices for an after theater light meal? Any other suggestions?
You can forget about Spice Market. Alta serves Spanish tapas so it is smaller in size (if that is what you meant by "light" meal). Del Posto Enoteca is not light by any means. It is a four course meal and when I had it last time, I was quite full after the pasta. Flavor-wise, I think Del Posto is better than Alta, though it could be just a matter of personal preference.
Any of them would be great if you ordered off the appetizers menu (or the tapas menu at Alta). I haven't eaten at Del Posto, but as between Alta and Spice Market, for my money, I'd go with Spice Market. Personally, I like the food at SM much better and appetizer portions are more generous than the tapas portions at Alta, though they are similarly priced.