I haven't tried the true high end mx series, like the 980 or 985. I used to own the 880 but I'm not even sure if you can get them anymore. I think the 880 was a slight step up of the 580 in overall sound quality. bass was decent. If you're looking for an earbud workout headphone I am also highly recommending the px685. It's a very unique design. Like a full size headphone with earbuds attached to the ends. I might be going out on a limb with this one, but they sort of remind me of the px200ii. A review is in the works. I'm actually thinking about starting a workout review thread and see if we can't get some non audiophiles to jump in and review their favorite workout beasts.
And I am with you, I am not a fan of in ear headphones at all. I love earbuds. Comfortable, decent sound. The only thing they lack is bass. But there are work-arounds for that.