I don't know the others, but Gowan's good. I've never heard any of his music, except the except his website, but I've seen him live with Styx five times now, and he is great. And while some (not all) Styx fans don't like his singing or stage manner, noone's complaining about his keyboard playing. And I think that says a lot.

My favorite keyboardist is REO's Neal Doughty. I personally really like his playing style, which is different from typical AOR keyboard playing (and REO aren't exactly a typical AOR band, but, they get enough AOR airplay that they definitely qualify as AOR). One thing I really like about Neal is that even in the 80s he never overused the synthesizer. I'm not a big synthesizer fan. But Neal only used synth when it's a real plus to do so, and otherwise stick to piano or hammond organ.