So far, anything I've heard except perhaps King of Terrors and the chorus on Orion - The Hunter. The first one just reminds me of PAntera, which is something I don't want when I listen to Symphony X. The vocal line on the chorus of the latter just strikes me as, well, bad.
Tha Accolade II, on the other hand is just fantastic. As is all the Ayreon records his on, and of course Star One.