Going forward it may be better to ask about the Realiser in this thread. http://www.head-fi.org/t/418401/long-awaited-smyth-svs-realiser-now-available-for-purchase/1275
Yes you will need the Realiser and ear mics when you make a PRIR, also its helpfully to know what the numbers mean that are displayed on the Realiser after you made the PRIR. Yes you will have to connect the Realiser to the speaker system, the Realiser sends out a bunch of different tones and verbal directions that are played back though the speaker system and those tones are what the ear mic's pick up and send to the Realiser to make a PRIR.
No you don't have to bring your headphone and gear but it would be a good idea if you did. You can compare what you hear from your PRIR and headphones to make sure its the same thing you hear coming from the speakers. Most can not tell that there headphones are on and speakers are off when they first compare what there new PRIR to the speaker system.
Yes it will work with IEM's but you can't make a HPEQ for the IEM's, you need the mics in your ear canal to make a HPEQ.
imo, if you are going to use the Realiser mainly for 2CH audio its a bit of a waist. Not to say for 2Ch stereo the Realiser is bad, its just that it excels at MCH. That said I do use my Realiser for 2CH stereo most of the time, because how my rig is set-up (i get lazy when I am relaxing) .
The Realiser is made for the pros that do the audio mastering and mixing for music and movies. What they do is make many PRIR's from all kinds of audio systems and room acoustics, when they do there mixing and mastering they can do it at home and hear how the audio sounds using different speaker systems and acoustics. Beware the Realiser is not really a plug and play toy.
btw, I hope PS audio has improved on there power cords. I had two of there top of the line power cords (the ones with about 20% silver) and they were awful. However I do like there P5 it does a nice job in my system.
I use Blacksands violet Z1 power cords and Iron Lung Jellyfish power cords. The Violet Z1 is very fast, clean and good sound-stage, the ILJF is much cheaper but a great bang for the buck and has is about 90% of what the Z1 sounds like. imo