If Zappa and related Mothers material counts, I've been listening to mostly his/their stuff from '72-'79ish. "Apostrophe" seems to be both a genuine progressive album and a parody/pastiche of what was considered progressive at the time, could probably say the same about Sheik Yerbouti (latter is probably a bit too heavy on the comedy for most folks here, maybe). Both with insane instrumentation and some genuine surprises amidst hard rock sections that give Sabbath and Floyd a run for their money in addition to some bizarre and humorous lyrics and just a touch here and there of sincerity. I dig Zappa's obsessive attention to detail, reliance on editing to produce a final product, and the use of sounds/sound effects "for their own sake."
I've tried to appreciate King Crimson and just couldn't enjoy it, at all.