I think it must be Spyros, not Speros. Very often, immigration offices made mistake. My fathers family name was then written in 3 ways: greek g becomes j, greek T becomes D. I heard from other greeks too that the greek letter B (pronounced V) was often kind of confusion.
All this to say you that all is possible. Also immigrants changed a little their names for better integration in the new country. Example:Zanetakis becomes Zane.
I found my grandmothers maiden name in a marriage certificate of my father.
The best information is from old people in the family. They remeber little things which are hapefull in searching.