Maybe try Rush, Yes, Jethro Tull, or the Moody Blues? I'm not an expert on King Crimson by any means but those four are all well-known progressive rock bands that would fit in a similar category (I know Rush cites them as an influence) and that have good music. The first prog rock band that came to mind would've been Pink Floyd but you already mentioned them.
Hope I was (somewhat) helpful! ^^
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