I like Embrace The Galaxy the best, but The Astral Episode is a great album as well. Like I said, I don't have the very latest Space Odyssey album so I can't comment on that one. But if you like Embrace The Galaxy, you'll dig The Astral Episode.
As for Time Requiem, they're more of a Malmsteen kind of power metal band. Very over-the-top with the guitars and keyboards, but solid performances from all. Unlike Malmsteen, I think they have great songs. There's also a heavy neo-prog influence.
I don't actually own Optical Illusion, so we should both buy it HERE. It's $6. Sweet deal.