I am not much of a fan of Glass Hammer per se, but I do enjoy their last release, Culture Of Ascent. They changed lead singers on this one.

I wouldn't say Ritual is exactly like Yes either, just 'ish'.

If you like Nightwish and the like, here's one for you:
Kingfisher Sky
http://www.myspace.com/kingfishersky - click on 'music' and they have full samples. Be sure to surf on down the page for 'live stuff'. My #1 prog album of the year.

And by all means, look up more than one Flower Kings video on Youtube if they've put you off in the past.