I have a 128GB SSD for the o/s and 3TB HDD for games, videos, music, which seems to work well as I like a fast o/s start up and fast apps launch, but willing to wait a few more seconds for games. I'm playing BF4 regularly, which takes over a minute to load from HDD so moved this to SSD which made a big difference loading and between rounds. Ideally a 256GB SSD would have been better, perhaps when they drop below $150.
Steam and Origin make it more difficult to move games from one place, but I found an easy way with Origin, not sure about Steam yet.