Of those I'd choose "groups eye oh" - "groups eee oh" sounds a little too Italiano to me, or too much like like the diminutive "oopsy-oh".
I'd go for "groups eye oh" too. I don't pronounce punctuation (where's Victor Borge when you need him?).
I did look up where the IO domain is, and it's the British Indian Ocean Territory (Diego Garcia &c). I was beginning to wonder if the server was somewhere near Jupiter!
