I also dislike blondes. I've shot plenty of SIGs, just don't like them that much. And I HATE the SIG 556 rifle too.
But I love AR-15s, so there you go. The M400 has a lot of nice features, it's basically the poor man's KAC SR-15. I would personally get rid of the SIG upper and get a BCM or DD or something along those lines. I'm not a fan of the 16" barrel with carbine gas system. Then again I have an SBR lower so I have a lot more options.