Output to Studio Monitors

I have an iMac and use the 1/8" analog stereo out to the stereo _line inputs_ on an amp & speakers. The sound is fantastic, and it's a lot simpler than anything USB. I don't see any reason to go to XLR unless your equipment requires it.

The audio out on the iMac can handle both headphones and line level. It really doesn't matter what kind of plug you use on the other end of the cable - RCA, TRS or XLR. What matters is the _nature of the input._

Powered speakers normally have their own amp inside, so going 1/8" iMac out --> 2xTRS line-in in should work fine - of course that assumes that your 'powered speakers' are actually that, and not just plain speakers that have 1/4" TRS inputs, expecting a speaker-out feed from an external amp.

The issue with XLR is that XLR inputs are usually intended for mic-level signals, so the line out from the iMac may be too much for your XLR inputs unless there's a trim/gain adjustment on the XLR inputs. Some devices have these trimmers, some don't.