@MrBoat, I've been just leaving mine on, but for a desktop setup, a power strip may be the easiest solution.
I'm not one to normally leave things on, but they seem not to draw much current when not in use (based on temperature). As you noted, they barely get warm when being played. When not being played, I didn't notice any heat from them.
I like their sound better than the Audioengine 5, but the 5+ is supposed to be improved. Also have the sense that the 305's would go much louder (which is often a moot point for a desktop). However, the AE5's definitely are designed for consumer use with the USB port, volume up front, etc.
Probably the most impressive thing about the 305's is the dispersion of the waveguide. While TheWarrior and ATLAudio were seated in the LP, I picked up one of the 305's off of it's stand and tilted it every which way up to about 30 degrees off axis. They did not hear any variation in the sound character! But, again, that is not of great benefit in a traditional desktop setup.
Lastly, one benefit of a well designed studio monitor is that the amps are designed exclusively for each driver. This allows the manufacturer to make it pretty bullet-proof just like the better designed subwoofers...the amp can limit before going into clipping.
Also, crossover resistance happens at low-level before the amps due to the active design. I don't know if this really matters, but intuitively, it seems like it is better than giving the signal extra juice then running it into the crossover. If nothing else it seems it would be more efficient since the resistance is being applied to much smaller power load.