King Crimson seems pretty interesting. I don't think length will be a problem with most of their songs. The 10 minute rule is a really rough estimate mostly to avoid something like Tales of Topographic Oceans or Thick as a Brick. It's also not so much the length itself as it is the time investment one song takes, I am not likely to listen to a song much if it is really long due to time constraints.
Is King Crimson's 90s and later stuff worth a listen ? I have been researching New Standard tuning and the Chapman Stick and it appears a lot of their newer stuff uses both so I am a little curious.
The Mars Volta seems a little closer to my tastes particularly with all the non-rock influences tossed in.
I am probably going to try and familiarize myself with both bands, though they aren't exactly what I had in mind.
If it sounds like I am being a bit difficult it's mostly because I have got a very specific sound in mind, which may or may not exist. Like a combination ofthis and this, perhaps with a some synths liberally tossed into the mix. I am not sure if anyone relate to having a specific style pre-made into their head, but that sometimes happens with me.