I just heard a friend's pair briefly out of my MCTH with an RCA 7308. Compared to my HD650Ms, my initial impression is I like the 58X sound sig more. Similar to @Outerspace Wasabi's impressions, more sparkle and bite up top and tighter, deeper, punchier bass. I think part of it is my pads are worn and mushy, exacerbating the mid bass hump. Another factor is brain burn from listening almost exclusively to my new Clears. I'm going on vacation but when I get back I'll borrow them for a longer listen and swap the pads to see how much difference that makes.