PAXfips & ChickenHouse. I don't know what SSH is. Should I be concerned? I just hit the space bar to wake it up, use it, and put it back to sleep. I do shut down the iMac once a week or so as I think that's likely good practice.
My HD is the 1GB fusion drive, overall machine usage speed is ok for me now on El Capitan.
I'm intrigued by the prospect of 'Siri', I gather that's voice control or interfacing or some such.
I'm not convinced I need any of it, but if I chat to Apple support as I do occasionally they may not want to deal with me if my iMac is not running the latest suggested software, and I do find the Apple support chatline superb.