Absolutely. Check Point's branded boxes are just open servers with weird PCIe slots. Take a look at the datasheets for the 15600, 16200, QLS250, etc. Very roughly, they say 16 GB supports ~6M connections, 32 GB supports 8-12M, 64 GB supports 16-25M, and 128 GB supports ~32M. Newer datasheets revise the connections per gigabyte down as new features consume some RAM.
The important thing to keep in mind is that the OS consumes some amount (generally fairly constant, and generally goes up a little with each major version), and the features you enable consume some amount per instance of the feature (i.e, per VS with it enabled).
RAM is cheap. If you're building a firewall for a given connection capacity, go with the 200k per gigabyte (or even 150k per gigabyte), give yourself an extra 25%, and round up to the next stick you need for optimal bank interleaving.