Sverd - The best of the bunch when loked at individually, but his playing probably wouldn't work for Opeth. It's too...fiddly.
CoB guy - Awesome technically, think he's very talented, TOTALLY wrong for Opeth.
Andy Winter - Too pianistic. Very emotive pianist and creative songwriter, but Opeth requires someone who can blend in with a variety of sounds, rather than someone like Winter who
demands to be centre of attention.
Steven Wilson - Too busy to commit.
Lazarre - Would have been perfect. Master of organs, great with a variety of sounds. Creative, but not overbearing (he knows how to be part of a band). Would have been my choice, so long as he didn't start singing
All of those listed are better keyboard players than Per, perhaps with the exception of Steven Wilson (and totally non-metal keyboardists like Tori Amos and Matt Bellamy are even better). But Larzarre aside, I think Per fits the best with Opeth. And he
nails organ sounds. I love it when he plays organs
Btw, Jordan Rudess is vastly overrated. He's waaaaaay too self-indulgent. Just listen to 'Endless Sacrifice' and you'll hear why in a short passage that damn-near ruins the whole song.