I don't think the MIracle and EX1000 are too similar. The Miracle is smoother and a little warmer, with less strident upper midrange and treble. I don't think you'll get much more mid-bass out of the Miracle so it may not quite satisfy in that respect but it rolls off less in sub-bass. It's also almost as spacious as the EX1000 without losing its excellent depth and layering (which the EX1000 can't quite match).
I don't really know much about the RE-600 at this point. I think I should finish the RE-400 review first before making additional plans. I don't think I can fit in an additional stint with a CKS1000 at this time, either. If it's leagues ahead of your MG7 I might change my mind, though
Sure I'll let you know.