Here in my studio, EVERYTHING has to pull AC through Furman conditioners. I consider them 100% essential here in the Midwest, given the kind of insane storms we have here. They won't withstand a direct hit on my AC line, but they do well at stopping spike transients that really aren't good for electronics.
My other key here is grounding. The entire studio is set up to be "star grounded" at the mixing desk's star ground point, and I use 16ga stranded wire to connect ALL chassis of rack gear and, by them being connected at the racks that have their Furmans, I can also maintain that star ground through the synths and other devices.
I consider both of these to be totally essential. The conditioners lower your overall e-noise in the studio's audio, plus the grounding method makes ground looping pretty impossible.