You should see the comparison chart over at e-on to see if it is worth upgrading. I used to have 5 esprit, and after a while, I felt I needed more control over lighting. I then bought the LightTune module, and this was really worth it, so many more features that can change dramatically your renders. To create my own plants, I then decided to buy Botanica, I ended up buying them all!
Now there is an Ecosystem module and a Hypervue module. It's really up for you to see what you really need. But chances are, you'll want them all. If you get the ecosystem module, and want more control over the ecosystem materials, chances are you'll want to get the Deep Access module too ( or is it called Advanced browser?), so if you can afford the big leap to PS in one shot, go ahead, at the end it is cheaper, if you can't, buy modules one by one, a bit more expensive, but  you do it at your own pace.