Upgrade your ram only if your projects limits your current ram,otherwise you will spend money for no reason.
Reason has an indicator that lights up when the hard drive cant handle the workload. So this is not your case.
REs are CPU hungry... and they suck the blood of that old macbook pro.
If you are a producer get an i7, but if you are apple's fanboy and don't have enough money go to the i5 solution and buy in two years or so an other mac.
I build my own pc ugrating old parts to i7 3770k overclocked @ 4.5 GHz / 8 B gb of 1600 hz ram / 240 gb ssd, two 23'' monitors for less than 900 euros, and I have a killer system, I can through limitless effects with no issues.
but yes I know... macs looks good.... lol