Any good audio opamp should be able to be configured as a follower amp so you can drive however many lines from a single source (a follower amp driving each) without any gain.
If you want over-current protection, you just need to look at the output spec of your chosen opamp and add a series resistor that keeps the full scale output below that current - probably on the order of 50-100 ohms, depending. If you're talking about ground isolation to eliminate added hum, you're going to need transformer coupling or some similar method - much more complicated and harder to get right, especially if your device has its own power supply, and may be less of an issue with your own installation.
The devices you are running are high impedance (high resistance even to AC signals like sound waves), so in normal operation, the opamp will drive very little power through the load to maintain signal levels. You only need amplifier ICs for very high voltages or, more commonly, low impedance drives (like an 8 Ohm or less speaker), a line level input is designed not to need much power to be properly driven.