Hey man, first of, let me tell you that Ibanez RG2550Z is a great axe my friend. It will suit you very well for prog music. Hell, Petrucci used to play Ibby's and he is nowadays considered (by many) the king of the genre (don't know which wood actually....). Some of Vai's Jems are basswood also, but he doesn't usually use mahagony guitars, at least not live.
As far as basswood vs mahagony goes, it's really a matter of preference. Now that mahagony gives a warmer, fatter sound whereas basswood is considered to be very balanced. I would actually say that basswood would fit prog music better, provided you're a solo guitar player.
The only thing I don't like on the guitar is the new trems, but that's also a matter of preference as I hear they are very good quality and stay in tune awesome.