Definitely not worth even ATTEMPTING to do SLI with two GTX 960's. Fortunately, getting better performance is going to be pretty easy because just about everything outperforms that card these days.
For the prices in Australia, you don't have enough to do a platform upgrade AND upgrade the graphics card to a model that is going to give you what you need. So I would recommend that you do THIS first, and then save the rest until you have enough to do the second part. By then though, there may be much better options on the table because there are new Ryzen parts coming supposedly in November or December and depending on when it is, there might even be 10nm Intel desktop parts by then, although I think it's doubtful that anything worthwhile...