My reasoning for two was to not just have Random Hunter-Gatherer Barbarian Tribe #s 1-46 to encounter as civilization expands. Perhaps two loci rather closer together?

Also, which way does the planet spin? If it's the same as Earth, Pseudo-Peloponessos isn't going to get very much in the way of rain or rivers probably, due to the huge mountains to its West/Northwest; weather systems bunch up on the western edge of the mountains and dump all their water there, which then creates rivers on that side. If it's opposite to earth, we've got a much better shot at it being reasonably moist there, but not utterly soaking it, which would put it quite in line with most of our examples of early civilization: Egypt (desert but with huge river), Sumer/Mesopotamia (near-desert but with two huge rivers), Northern China (dry-ish area next to desert with a reasonably-sized river), and Mesoamerica (started in the tropical plains of the Gulf of Mexico).
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Also, for the second location, I was thinking along the opposite end of the E-W mountains Pseudo-Peloponessos sits below, possibly including the island just south of it.