The booklet, and one of the special edition videos I saw, Romeo and Allen talked about Rod Tyler. For starters he has a very shy stage presence apparently, he didn't/couldn't do live shows for wtv reason. So the band would not have made it very far with Rod Tyler for that reason, and he personally knew this and actually introduced the band to Russ. And I shit you not, he said something along the lines of "I can't do this anymore guys, but I know this singer, who aint quite as good as me, but really good none the less." And thats how it went down, there where no hard feelings with Rod. I don't think he is a bad singer, I just don't think symphony x is his fortee. But Russell Allen is god, f'ing golden trade off. Be like trading some nobuddy for Jorn, can't get any better than that.
I don't know the entire story, or who it envolved, but officially Rullo stated he was "having some troubles with the band" He didn't point out any members in particular. But the fact he is there and happy now, I would assume it was with Miller. Either that or they worked out there indifferinces.