To be more clear, what a firewall is going to want more of is:
fast NICs (especially ones that don't need CPU power to run) - I like Intel-powered ones CPU RAM
not necessarily in that order. All an SSD will do is make it boot faster. You can tell if you need more CPU by running top while the firewall is "slow" and seeing if the load average is well in excess of 1.
Assuming the firewall is your problem to begin with.
If you want to see if you are bottlenecked on the storage subsystem (so an SSD would improve things) then run iostat and see how busy the drive gets.
It is feasible if your firewall rules are logging tons of stuff that you are running in to storage issues, but far more likely is what others have posted - NICs and CPU. I'd actually suspect just your Internet bandwidth in the first place rather than any firewall bottleneck.
Actually I’m not having a problem. Just was wondering if the ssd would have any impact. It seemed to me once it booted, that there was very little reason to go back to the hard drive for much, but I thought it would be worth getting other opinions. - thanks