The following tests were conducted to see how much difference a RAM (memory) really makes in general system performance.
Our test system was ASRock Extreme 4 Motherboard with an i7-4770 and a GTX660.
We started with 8 gig of RAM then doubled it to 16gigs and then doubled it again to 32 gigs.The benchmark program we used was Passmark PerformanceTest
As you can see the increase in performance is very marginal.
Extra RAM will help in keeping multiple windows open at the same time and certain programs also benefit from more RAM like large files in Adobe Photoshop.