You could use your SSIA to invest in the PRSA, however you will be restricted by the age limits as to the amount you can save in any one year e.g. Age to 30, 15% of earning, 30 to 40, 20%, 40 to 50, 25% and 50+, 30%. You can claim rax reliefs up to these limits in the basis of your current rate, 20% or 42%.The government might do something to persuade people to use their SSIA, for example grant relief to everyone at the higher rate. You could also surrender your savings policy (make sure to check to cost of doing so isn't prohibitive) and invest that in your PRSA.
There are many other savings options, but tax wise putting into the pension is the best solution.